PDFx is an open, backwards compatible extension of PDF that bundles many documents into a single file, plus a minimal desktop viewer for macOS and Windows.
A .pdfx file is a fully valid PDF: open it anywhere and every page shows in sequence. Open it in PDFx and it splits back into the original documents. Plain single PDFs work as they are.
Drag and drop .pdf or .pdfx files anywhere in the window. Each document renders as a horizontal strip of pages, and documents stack vertically. Reorder or remove them, then Export .pdfx to save the whole collection as one file.
See SPEC.md for the format. It is short: the entire trick is one embedded JSON manifest.
Built with Electron, Vite, TypeScript, and React. PDF rendering by pdf.js, assembly by pdf-lib.
yarn # install
yarn dev # run in development
yarn build:mac # package for macOS
yarn build:win # package for WindowsMIT