Merge PDF

Merge PDF combines several PDF files into a single PDF, in the order you choose, without sending them anywhere. It is for anyone who needs one file where they have several: a job application with a CV, cover letter and certificates, a set of scanned receipts for an expense claim, or chapters exported separately that belong in one document.

The merge runs in your browser with pdf-lib, an open-source PDF library written in JavaScript. Each file is opened and checked, then its pages are copied, one file after another, into a brand-new PDF. A page is copied as it is — its text, fonts, images and vector drawings are not re-rendered or recompressed — so text stays selectable and searchable and images keep their exact quality. Each page keeps its own size and rotation, which means an A4 letter, a US Letter form and a landscape slide can sit in the same file, each page at its original dimensions. Web links on the pages keep working, and a link that jumps to another page of the same file is re-pointed at that page in the merged document.

Some things belong to a document rather than to its pages, and those are not carried over. The merged file has no bookmarks (the outline panel), because each original outline points into its own file. Fillable form fields still show what was typed into them, but they are no longer a working form. Files attached to the whole document, accessibility tags and digital signatures are dropped — a signature could not stay valid anyway, because signing covers the exact bytes of the original file. Title and author metadata is not copied; the new file lists AllUtil as the software that produced it.

Password-protected and permission-locked PDFs are refused with a clear message rather than merged into a file with blank or broken pages: the library cannot decrypt them. Open such a file in a PDF reader with its password, save or print an unprotected copy, and merge that. Up to 100 files can be merged at once, each up to 200 MB and 500 MB in total — everything happens in your device's memory, so those limits are about keeping the browser tab from crashing.

Nothing is uploaded. The files are read into the page, merged there and handed back to you as a download. You can confirm it in your browser's developer tools: open the Network tab, merge some files, and no request carries your PDFs (the site does load its own scripts and analytics, which never include your files). That matters for exactly the documents people merge most — contracts, bank statements, ID scans and medical records.

1. Each file's first bytes are checked for the PDF signature (%PDF-), so an image renamed to .pdf is named as what it really is before any work starts. 2. Each PDF is opened with pdf-lib. A file whose trailer declares encryption is refused, and a file that cannot be parsed is reported by name as damaged. 3. Internal links are prepared: a link's target page is recorded by position (named destinations are looked up first), and back-references from annotations to their page are removed, so copying one page never drags in hidden copies of others. 4. All pages of each file are copied, in queue order, into a new PDF with pdf-lib's copyPages. Page size, crop box and rotation are copied with the page, including values the page inherits from its document. 5. Links are re-pointed at the copied pages, the document is saved with compressed object streams, and you download merged.pdf.