How merging works here
A PDF is a collection of page objects, each pointing to the fonts, images and drawing instructions it needs. Merging copies those page objects, with everything they reference, from each file into a new document, in the order you set. Nothing is printed, rasterised or re-compressed: text stays selectable and searchable, vector graphics stay sharp at any zoom, and photos keep their original resolution.
Because pages are copied as they are, page sizes are kept too. You can merge an A4 contract with a US Letter invoice and a landscape spreadsheet printout; each page keeps its own size and orientation in the combined file.
How do I put the PDFs in order?
Files are merged top to bottom in the list. Use the arrows to move a file up or down and the ✕ to remove one. Every page of each file is included, in its original order. To leave some pages out or change their order within a file, run that file through Split PDF first (type the pages you want, in the order you want), then merge the result.
Each file shows its page count, so you can check at a glance that the merged PDF will have the number of pages you expect.
What carries over when merging PDFs?
Pages come through exactly, but a few document-level features belong to the original files rather than to the pages:
- Kept: text, fonts, images, vector graphics, page sizes and rotation, and links within a page.
- Not kept: bookmarks (the outline in a PDF reader's sidebar), because each file's bookmarks point into that file.
- Fillable form fields may lose their interactivity. To be safe, fill and flatten forms (or print them to PDF) before merging.
- Digital signatures no longer validate, because the signed document has changed. Merge first, then sign the final file.
Password-protected PDFs
Encrypted PDFs, including files that open without a password but restrict printing or editing, can't be read until the protection is removed. Open the file in a PDF reader with the password and save or print a copy as a new PDF, then merge that copy. The tool tells you which file is protected, so you know which one to fix.
Typical uses
People most often merge PDFs to:
- Combine scanned pages of a document that the scanner saved as separate files.
- Assemble an application: CV, cover letter, certificates and ID in a single upload.
- Collect a month's invoices or receipts into one file for an accountant.
- Join chapters, handouts or slides into one reading pack.
- Attach supporting documents to a contract or report.
Private by design
Online PDF tools usually upload your files to their servers. This one runs pdf-lib, an open-source PDF library, inside your browser: the files are read from your device and the merged PDF is built in memory. Contracts, bank statements, medical records and IDs never leave your phone or computer. There's no account, no watermark and no limit on how many PDFs you merge.
Can I merge PDFs with apps I already have?
On a Mac, Preview can merge PDFs: open the first file, show thumbnails in the sidebar, and drag other PDFs or pages into it. On iPhone and iPad, the Files app can combine documents: select several PDFs, tap the ••• button and choose Create PDF. Windows has no built-in way to merge PDFs, which is where a browser tool like this is most useful. It's also handy on Chromebooks, shared computers and anywhere you can't install software.
The advantage here is control: you see every file with its page count, reorder with one tap, and get a PDF whose pages are copied exactly rather than re-printed.
How big will the merged PDF be?
A merged PDF is roughly the sum of its parts, so ten 3 MB scans make a 30 MB file, too big for many email accounts and upload forms. Scans are usually the heavy part: scanning at 150–200 DPI instead of 600 DPI, or in greyscale for text documents, makes each page several times smaller. If you're building a PDF from photos of documents, compress or resize the photos first, then turn them into a PDF with Image to PDF and merge.