PROS 1.5.1

PROS is a free, open-source Windows desktop utility for processing PDF files. It can remove known PDF passwords, aggressively compress PDFs, convert supported colour content to grayscale independently of compression, join multiple inputs, split an input at validated page boundaries, and write predictably named results without changing the source files.

The release is a single windowed PROS.exe. It uses Python's Tk interface and pikepdf/qpdf. The tkinterdnd2 wrapper and its bundled TkDND extension provide native Windows File Explorer drag and drop. PROS does not use Qt, PySide, or PyQt.

Official Windows builds are provided without charge on the GitHub Releases page. Each release keeps the one-file portable format and links the executable to its matching source tag and checksums.

Run the application

1. Copy PROS.exe to a local folder on a 64-bit Windows 10 or Windows 11 PC.
2. Double-click it. No Python installation or administrator access is required.
3. Complete the numbered workflow from top to bottom: select a file arrangement and any additional processing, add the input PDFs, choose the output, review the job, and then process it. Split inserts Choose where to split as step 3 and renumbers the remaining cards, making a six-step workflow. Required steps remain red until complete and then turn blue; Process turns blue only after the job succeeds.
4. Add PDFs with the file picker or drag them from Windows File Explorer onto the input area. Keep separate and Combine accept multiple files; Split accepts one. Click the already-selected arrangement a second time within four seconds to open the picker again.
5. Supply passwords for encrypted inputs when needed, choose an output folder, and confirm the displayed order. A multi-file Keep separate job derives each output name from its corresponding source file, so the shared name field is disabled and labelled automatic.
6. Check the dedicated Review step, then start the job from the separate Process step. Keep the application open until it reports completion.

PROS leaves input files unchanged. Outputs are staged and validated before they are published to the selected folder.

Drag and drop in every arrangement

External file drag and drop is available in Keep separate, Combine into one PDF, and Split one PDF. Dropped PDFs enter the same existence, regular-file, .pdf, duplicate, and capacity checks as files chosen with the Add control, and both routes preserve the submitted order. Keep separate writes one output for each input in displayed order. Combine uses that order as the final page order; use the Up and Down controls to adjust it. Split remains a single-input operation. The ordinary file picker remains available as a keyboard-accessible alternative.

Keep separate is a processing operation, not a duplicate-file command: select Remove password, Reduce file size, Convert to grayscale, or a combination before starting it. Multi-file outputs apply the same selected processing to every input.

Drop paths are handled as Windows/Tcl file lists, including multiple files and paths containing spaces or non-ASCII characters. Folders, non-PDF items, unavailable files, duplicates, and files beyond the twelve-input Keep separate/Combine limit are not accepted. Split does not accept a second input. Drops are refused while a job is active or the selected arrangement is full.

Run PROS normally rather than as administrator. Windows generally blocks File Explorer, which runs at normal integrity, from dropping files into an elevated application.

Compression, grayscale, and progress

PROS uses one aggressive compression profile: the profile previously called Ultra. It rewrites PDF structure, uses a JPEG quality target of 65, and may downsample supported large raster images toward 150 DPI. Compression is lossy; fine image detail and small scanned text may become softer. Always inspect important outputs before discarding any separate working copies.

Grayscale converts supported embedded raster image objects and common DeviceRGB/DeviceCMYK colour operators in page and nested Form content. Ordinary text, vector fills, and vector strokes that use those common operators are therefore converted. ICC-based and spot colours, patterns, shadings, some transparency constructs, annotation or form-widget appearances, and masked or unusually encoded images may remain in their original colour. PROS retains such unsupported constructs and reports a warning so the output can be reviewed. Grayscale can be selected with or without compression.

Automatic suffixes are ordered Join, Pwd_Rmv, Cprs, then Grey, followed by Part N for split outputs. For example, compression plus grayscale produces Report - Cprs - Grey.pdf, while grayscale alone produces Report - Grey.pdf. A multi-file Keep separate job ignores the single shared base-name field and uses each input stem with its active processing suffixes; for example, Invoice A.pdf and Invoice B.pdf become Invoice A - Cprs.pdf and Invoice B - Cprs.pdf when compression is selected. If two inputs from different folders would produce the same Windows output name, preflight blocks the job so neither result can overwrite the other.

The interface uses the same active, inactive, hover, and disabled treatment for action and arrangement buttons. The + Add, - Remove, and Clear controls are grouped consistently at the bottom-right of the list they change; Split includes its own Clear control. Guidance, progress, success, and attention messages use a common bordered-panel style. Review and Process remain separate so choosing settings cannot accidentally start a job.

PROS does not show a pre-run estimate of runtime or output size. Progress shown at real processing boundaries and during saves comes from worker events. Between worker reports, the per-file compression meter advances periodically as a time-based guesstimate so the window stays responsive during native PDF work; it is not a byte-accurate measurement and can pause or advance unevenly. Worker events, the final completion message, and output validation are authoritative.

Keep enough free disk space for the input, staging files, compression candidates, and final output; several times the combined input size is prudent. Compression and grayscale processing may decode an embedded image into memory, where its size is determined by pixel dimensions and colour channels rather than its compressed size in the PDF. A document near the 180 MiB acceptance size can therefore need multiple gigabytes of temporary disk space and memory when it contains very large scans. Close other memory-intensive applications before processing such a document.

Brand assets

The main window header uses assets\PROS-Logo.png, and the About dialog uses assets\PROS-App-Icon.png. assets\PROS.ico supplies both the Windows executable/Explorer icon and the Tk window icon. All three runtime images are bundled inside the one-file executable.

assets\PROS-Logo.svg and assets\PROS-App-Icon.svg are the editable vector masters for documentation and future asset generation. They are bundled for release verification but are not rendered directly by Tk. Their lettering uses the Windows Segoe UI family with Arial and generic sans-serif fallbacks, so use the supplied PNG/ICO files when an exact, portable render is required.

Offline and privacy behaviour

PDF processing is local. PROS does not require an internet connection and does not upload PDFs, passwords, filenames, or usage information. A PyInstaller one-file application extracts its embedded Python/Tcl/Tk/native libraries to a random %TEMP%\_MEI... directory while it runs and removes that directory after a normal exit. The first launch may therefore be slower and may be inspected by antivirus software.

Building from source normally uses the internet to download hash-approved Windows wheels. That is separate from the behaviour of the finished executable. For an offline release build, prepare a wheelhouse on a connected Windows x64 machine using the exact Python version and audited lock file:

py -3.13 -m pip download --require-hashes --only-binary=:all: --requirement requirements-windows-x64.lock --dest wheelhouse
$env:PROS_WHEELHOUSE = (Resolve-Path .\wheelhouse)
.\build.ps1
Remove-Item Env:\PROS_WHEELHOUSE

Build PROS.exe

Prerequisites:

• 64-bit CPython 3.13.15 from python.org, including Tcl/Tk and the py.exe launcher
• Windows PowerShell 5.1 or PowerShell 7+

From the repository root:

Set-ExecutionPolicy -Scope Process Bypass
.\build.ps1

The build script requires a clean Git commit, recreates an isolated .release-venv, and installs only the exact Windows wheels and SHA-256 hashes approved by requirements-windows-x64.lock. It rejects extra distributions, verifies the audited Python, package, and native-library versions, runs the full source test suite, removes only project-scoped build directories, builds the one-file windowed program, and runs the packaged engine self-test. The release is:

dist\PROS.exe

It also compares every embedded outer-archive item, Python module, standard library ZIP entry, DLL, and data file with a reviewed allowlist. The build fails on an unexpected PyInstaller warning; absent legal, brand, PDF, GUI, or drag-and-drop payload; the unused ISO Schematron module or data; incorrect PE architecture/subsystem/icon resources; or a mismatch between the embedded Git commit and the clean source tree. No release verification stage is skippable. The script prints the executable's byte size and SHA-256 hash when complete.

After an intentional dependency, PyInstaller, or frozen-payload change, run .\build.ps1 -UpdateAuditManifests once from an otherwise clean commit. Review the exact warning and archive changes it writes under packaging, commit the approved manifests, and then run ordinary .\build.ps1 again. The update switch is maintenance tooling and never bypasses verification for an official release.

PROS.spec requires and bundles the five canonical brand files; the MPL licence; the exact-source, trademark, and asset notices; and the complete third-party notices. The Windows/Tk ICO, logo and application-icon PNGs, and both SVG masters remain available inside the one-file executable. The build fails instead of silently substituting PyInstaller artwork or omitting a legal document if any required file is missing. hook-pikepdf.py explicitly collects the qpdf DLLs vendored by the Windows pikepdf wheel. PyInstaller's standard Tk hooks collect Tcl/Tk, while the pinned pyinstaller-hooks-contrib hook collects only tkinterdnd2's Windows x64 TkDND DLL and Tcl scripts. No blanket Pillow, Tk, or multi-platform DnD collection is used. The unused lxml.isoschematron module and its data resources are explicitly excluded; normal lxml, pikepdf, qpdf, compression, and grayscale functionality remains included.

Prepare release assets

After committing and successfully building the exact source, create tag v1.5.1 at that commit and push the repository and tag publicly. Then run:

.\prepare_release.ps1

The script requires a clean Git working tree and proves that the local tag, public remote tag, and HEAD resolve to the same commit. It always performs a fresh hash-locked rebuild and confirms that the EXE FileVersion, ProductVersion, embedded commit, packaged self-test version, source files, and tag all agree. It then validates hash-pinned pikepdf and qpdf source archives and prepares the renamed Windows executable, exact tagged PROS source archive, third-party source archives, and SHA256SUMS.txt in a unique staging directory. The completed directory is moved into place only after every check succeeds, and an existing version is never overwritten. The ignored release directory is uploaded only to the matching tagged GitHub Release.

Packaged self-test

main.py dispatches --self-test before the application GUI is initialised. To rerun it:

.\dist\PROS.exe --self-test .\build\manual-self-test

The test creates a unique directory under the supplied path and generates two fixed colour image/vector PDFs. It processes the first once with compression plus grayscale and once with grayscale alone, checks the exact Cprs - Grey and Grey names, verifies that compression downsamples while grayscale alone preserves image dimensions, and checks common vector/raster grayscale conversion. It then submits both sources to Keep separate in a deliberately non-alphabetic order, requiring one ordered, reopenable, syntax-clean Cprs output per input whose name comes from that input's stem rather than the global base-name field. Every source hash must remain unchanged.

The test validates every bundled brand asset's release hash and image/vector metadata and writes selftest-result.json. The report records all five asset hashes and all three PDF jobs. It also creates a withdrawn Tk window, loads the bundled Windows x64 TkDND extension, verifies the exact nine-file DLL/Tcl payload, and records the reported Tcl, Tk, and TkDND versions. No interactive window is shown and the test makes no network calls.

For release acceptance, also test on clean, offline Windows 10 and Windows 11 x64 virtual machines that have no separate Python installation. Exercise paths containing spaces and non-ASCII characters, an encrypted PDF, invalid/corrupt input, a read-only output folder, cancellation, aggressive compression, grayscale alone, compression plus grayscale, and a representative PDF larger than 180 MiB. In the frozen executable, drag PDFs from File Explorer into every arrangement, including paths containing spaces and non-ASCII characters. Confirm one ordered, source-stem-named output per input for multi-file Keep separate, the displayed and output order for Combine, single-input enforcement for Split, and the twelve-input limit. Reopen every resulting PDF with an independent viewer and preserve the source SHA-256 before and after the test.

Development checks

.\.venv\Scripts\python.exe -m pytest -q
$env:PROS_RUN_LARGE_TEST = "1"
.\.venv\Scripts\python.exe -m pytest -q tests\test_large_file_acceptance.py
Remove-Item Env:\PROS_RUN_LARGE_TEST
.\.venv\Scripts\python.exe -m ruff check .
.\.venv\Scripts\python.exe -m piplicenses --with-license-file --with-notice-file

Inspect build\pyinstaller\PROS\warn-PROS.txt after each dependency upgrade. Unexpected missing imports must be resolved before release. Do not add blanket --collect-all PySide6 or other Qt workarounds; Qt is not a PROS dependency.

Licence

Copyright (c) 2026 David Coetsee and PROS contributors.

Except where a file or notice states otherwise, PROS-authored source code, documentation, and original asset files in this repository are licensed under the Mozilla Public License 2.0 (MPL-2.0). MPL-2.0 applies at the file level: changes to MPL-covered files that are distributed must remain available under MPL-2.0, while those files may be combined with separately licensed code.

The PROS name, logo, wordmark, and application icon identify official project releases. Their copyright is covered by MPL-2.0 where they are PROS-authored project files, but MPL-2.0 grants no trademark rights. See TRADEMARKS.md for permitted brand use, including unmodified redistribution and clearly identified forks.

Third-party components are not relicensed under MPL-2.0. They remain under their respective terms, which are recorded in THIRD_PARTY_NOTICES.txt.

Each official binary release must identify the matching repository tag or versioned source archive from which it was built. Anyone distributing PROS in Executable Form must comply with MPL-2.0 Section 3.2, including informing recipients how they can obtain the corresponding MPL-covered Source Code Form by reasonable means in a timely manner.

Third-party software

Copyright, licence, attribution, and source-availability information is in THIRD_PARTY_NOTICES.txt. The same file is embedded in PROS.exe. The notices describe the pinned build represented by this repository; regenerate and review the dependency inventory whenever any package or CPython build changes.