Open Source Alternative to Adobe Acrobat, with a hopefully familiar UI

What shipped: Open PDF Studio — a free, MIT-licensed PDF workbench for Windows. Twelve tools (organize, comment, fill & sign with real digital signatures, form prep, true redaction, OCR, compare, encrypt, optimize, repair, watermark, export), Acrobat's keyboard shortcuts verified against Adobe's published table, and every whole-file operation doubles as a CLI subcommand. No ads, no telemetry, no upsells. The goal was at-or-near 1:1 with Acrobat's everyday feature set, and if you daily-drive Acrobat, the muscle memory should just work. Repo + installers: github.com/jasonulbright/Open-PDF-Studio The fun part is how it got built. I started by asking Fable 5 to write the prompt I should give it. Then I fed its own prompt back to it. It produced the full build plan and got to work — spawning Sonnet 5 subagents to review each phase, keeping a running list of deferrals, and re-ordering that list every few steps like a tiny project manager. Then I hit my weekly limit almost immediately, because of course I did. So the middle of this build belongs to Opus 4.8 and Sonnet 5 — they did the majority of the heavy lifting while Fable 5 sat in timeout. When the reset landed today, Fable 5 came back, worked the deferral list down to zero, and v2.0.0 got tagged the same day. Full disclosure: it didn't start from nothing. The base was SpectraPDF, an app I'd built earlier as a simple CutePDF alternative (minus the Windows XP-era UI). The jump from "splitter/merger with a nice theme" to "Acrobat-class workbench" is what the screenshots and the token bill are about. The receipts: four days, a bit over two billion tokens across the Claude family. The cost column is API-equivalent pricing — I'm on a subscription, which is both why this was affordable and why the weekly limit found me. And yes, there's a $1.55 GPT-5.6 line item in there. Every production needs a cameo. Feedback very welcome — especially bug reports.