OpenPDF
Application · PDF editor / Android & iOS · 2026
A reader that treats a PDF like a book and an editor whose changes Acrobat can open later. No account, no subscription and no uploading your file to someone else's server.
A free PDF reader and editor for Android with a true book mode, annotations that follow the PDF standard and full page management – everything stays on your phone, with no account and no ads.
Book mode places two pages side by side – automatically in landscape and on an unfolded foldable screen, because the app detects the hinge. The cover can be shown on its own, just like in print, and a spread can be zoomed and panned like a single illustration; when you zoom in, the visible area is re-rendered, so text stays sharp. On top of that: continuous scrolling or page turning, right-to-left reading for manga and RTL languages, and plain, night and sepia paper.
Editing covers pen, highlighter, text, notes, shapes and handwritten signatures saved for reuse. Everything is stored as standard PDF annotations with appearance streams, so a file opened later in Acrobat or a web browser looks exactly the same and can still be edited – these are not pixels burned into the page.
At the document level: rotating, deleting, duplicating and reordering pages, inserting other PDFs and images, merging files, forms including flattening, AES-256 password protection, exporting pages to PNG and JPG, and search that ignores diacritics. Undo and redo also cover page operations.
The whole thing is built on Kotlin Multiplatform and Compose Multiplatform: Android uses PdfBox and the system PdfRenderer, while the same UI code supports iOS through PDFKit. Every merge to the main branch builds and publishes a new release, and the app offers the update on its own.
Features
- book mode with foldable hinge detection
- standard PDF annotations, readable in Acrobat
- forms, signatures and flattening
- page operations with undo and redo
- requires Android 10 or newer
Technology
- Kotlin
- Compose Multiplatform
- Material 3
- PdfBox
- PDFKit
My role
Design, architecture, implementation and releases