What the Merge PDF does
Merge PDF combines two or more PDF documents into a single file. Add contracts, invoices, scanned forms, chapters of a report or lecture slides, arrange them in the right order with the arrow buttons, and download one tidy document that is easier to send, upload, print and archive.
The pages are copied exactly as they are. Text stays selectable and searchable, images keep their resolution, and every page keeps its own size and orientation, so you can even combine A4 and US Letter pages or portrait and landscape documents in one file. For each file the tool shows the number of pages before you merge, so you know what you will get.
Unlike most online PDF services, nothing is uploaded. The PDFs are read and combined by a JavaScript library running in your own browser, which makes the tool suitable for confidential documents such as bank statements, medical letters or ID scans.
When to use it
Applications
Combine your CV, cover letter and certificates into one PDF, as many job portals and universities require.
Invoices and expenses
Collect a month of receipts and invoices into one file for your accountant or tax return.
Reports and theses
Join chapters, appendices and a cover page created in different programs.
Scanned documents
Merge pages that your scanner or phone app saved as separate PDF files.
Tips for the best results
- Name your files with numbers (01-cover.pdf, 02-letter.pdf …) before adding them — it makes ordering quicker.
- If the merged file is too large for an email or upload limit, compress the images in the original documents first.
- Password-protected PDFs cannot be merged; remove the password in the program that created it.
- Bookmarks and form fields from the source files are not carried over; the visible content of every page is.
- Check the page count in the confirmation message to make sure every document was included.
How the Merge PDF works
The tool uses pdf-lib, a widely used open-source PDF library (MIT licence) that is hosted on our own server and only loaded when you open a PDF tool. When you add a file, pdf-lib parses its structure in memory to count the pages and detect encryption.
When you click “Merge PDFs”, a new empty PDF is created and the pages of each file are copied into it in the order of the list, together with the fonts, images and other resources they use. The result is saved as a standard PDF that opens in every reader.
Everything happens in your browser’s memory. The speed depends on your device; merging a few documents of normal size takes about a second.