Merge PDFs

Merge unlimited PDFs into one. Rearrange, rotate and preview pages.

Combine any number of PDFs into a single document, with drag-and-drop ordering, page preview and rotation. Completely lossless — page content is copied verbatim.

Merging does not degrade anything

A PDF stores its pages as independent objects. Merging copies those objects into a new document and writes a new page tree — the image and text data inside each page is untouched, byte for byte. You can merge and re-merge indefinitely with no quality loss whatsoever.

How to use it

1. Add all the PDFs you want to combine.
2. Drag them into the order you want. Files merge in list order, not the order you added them.
3. Preview pages and rotate any that are sideways.
4. Merge and download.

Things to check

• Order. The most common mistake. Verify the list before merging, not the output afterwards.
• Mixed page sizes. A merged document can contain A4 and Letter pages together. It displays fine but prints inconsistently, with some pages scaled. Normalise first if it is going to a printer.
• Orientation. Rotate sideways pages before merging so you only deal with it once.
• Total size. Merging is additive — three 2 MB files make a 6 MB file. Check the upload limit before assuming it fits.

A typical application workflow

Scan each certificate, build individual PDFs with Image to PDF, check each one is right way up and legible, then merge in the order the application lists them. Read the merged file end to end before uploading — that final check catches missing pages, duplicates and upside-down back sides more reliably than anything else.

Frequently asked questions

Does merging reduce quality?

No. Page objects are copied verbatim, so the merged document is byte-identical in content to its sources.

How many PDFs can I merge?

There is no fixed limit — the constraint is your device’s memory. Dozens of ordinary documents is comfortable.

Can I merge PDFs of different page sizes?

Yes, and the result displays correctly. It will print inconsistently, with some pages scaled to fit the paper, so normalise sizes first if printing matters.

Why is my merged PDF so large?

Because merging is additive and one source was probably already large. Deal with that file individually rather than compressing the whole merged document.

Can I reorder pages after merging?

Yes — use Organize PDF, which shows page thumbnails you can drag into any order. That is also lossless.

Are my files uploaded?

No. Merging runs in your browser using pdf-lib. Nothing is transmitted.

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