AI-built open-source Acrobat alternative ships 12 PDF tools free

Open PDF Studio is a free, open-source (MIT-licensed) PDF tool for Windows built to look and feel like Adobe Acrobat. It bundles twelve tools: organizing pages, adding comments, filling and signing forms with real digital signatures, preparing forms, true redaction, OCR (recognizing text in images), comparing documents, encryption, optimization, repair, watermarking, and exporting. Keyboard shortcuts were checked against Adobe's own published shortcut table, so someone used to Acrobat's muscle memory should feel at home immediately.

Every operation that works on a whole file also runs as a command-line (CLI) command. There are no ads, no telemetry, and no upsells. The code and installers are on GitHub under jasonulbright/Open-PDF-Studio.

The build process itself is unusual: the developer first asked Fable 5 to write the prompt that should be given to it, then fed that generated prompt back in. Fable 5 produced the full build plan and got to work, spawning Sonnet 5 subagents to review each phase and continually reordering a running list of deferred tasks like a small project manager. The developer then hit their weekly usage limit almost immediately, so the middle of the build was carried out mostly by Opus 4.8 and Sonnet 5 while Fable 5 sat in timeout until its limit reset.