PDF Reader & Editor
A full PDF reader and editor — annotate, sign, edit text, fill forms, lock, convert and scan.
- Annotate: text & area highlight, underline, strike-through and freehand ink
- Sign documents with a drawn signature you can move, scale and rotate
- Edit existing text in place and insert new text blocks
- Fill forms and add watermarks
- Lock / unlock PDFs with a password
- Merge, split, compress and manage pages
- Convert image ↔ PDF, PDF → image and PDF ↔ Word
- Camera document scanner with edge detection, crop and filters
// case study
Overview
A native Android PDF reader and editor. It goes well beyond viewing: you can annotate, sign, rewrite text in place, fill forms, protect files with a password, convert between formats and scan paper documents with the camera.
How it works
Rendering and most of the editing run on pdf.js inside an Android WebView, bridged to Kotlin. Editor modes (EDIT, ANNOTATE, SIGN, FILL_OUT, WATERMARK) are driven from Compose UI, and custom JavaScript patches on top of the pdf.js wrapper handle in-place text replacement (mask and outline layers), stamps and flattening on save.
- Signatures: drawn on a Compose signature pad (undo, width, colour), then placed as a stamp you can move, scale and rotate before it’s flattened into the page.
- Document tools: PDFBox-Android handles merge, split, compress and page management; Apache POI powers Word conversion.
- Scanner: CameraX capture with OpenCV and LiteRT for on-device edge detection, then crop and filters before building the PDF.
Architecture
Around 15 Clean Architecture modules with hand-written dependency injection (no Hilt), State/Action/Event screens, and a bleeding-edge toolchain (AGP 9, Kotlin 2.4 with context parameters, Compose BOM 2026, targetSdk 37).
Status
In active development: editor UX, signatures and text editing are being refined.
