What you need to know about merging PDFs
Things worth knowing before you merge
Once you've merged, the order is baked in. If you realize afterward that page 3 should have come after page 7, you'll need to either merge again (easy enough) or use the Organize Pages tool to rearrange after the fact. The point is: take thirty seconds to get the order right in the upload list before you click Merge. The drag-to-reorder feature is there precisely for that, use it.
Bookmarks and internal links inside your source PDFs may or may not survive the merge depending on how the originals were created. Page content always transfers perfectly. What gets iffy is interactive elements: form fields, hyperlinks within the document, and table-of-contents bookmarks. For most purposes, emailing a combined packet, uploading to a portal, sending to a printer, this isn't a problem. If you need the interactive elements intact, test the merged result before distributing it.
Your files are processed server-side in a session folder that only your browser can reach, not passed to any third party, and deleted within an hour. Uploading 30 signed contracts, a set of confidential exhibits, or a client's medical records here carries the same risk profile as attaching them to an email, low, but not zero. Use judgment based on the sensitivity of the material.
Frequently Asked Questions
There's no hard limit on the number of files. In practice, the constraint is the 50MB total upload ceiling, so you can merge as many files as fit within that. A paralegal merging 30 one-page exhibit PDFs will be well under it. Someone trying to merge five 20MB scans won't, in that case, compress the big ones first, then merge.
No, merging is non-destructive. Every page from every source file is copied exactly as-is into the new combined document. Images stay at their original resolution, text stays sharp, and nothing gets re-encoded. The only thing that changes is that everything is now in one file.
You can drag the files in the upload list into whatever order you want, each file's pages will appear in the merged document in that sequence. What you can't do here is rearrange individual pages across different files (e.g., put page 2 of file A between page 3 and page 4 of file B). For that level of control, use the
Organize Pages tool after merging.
You'll need to remove the password first. Use our
Unlock PDF tool, then come back and merge. The resulting merged file won't have a password on it, if you want to re-protect it, run it through
Protect PDF afterward.
The merged PDF will have pages numbered sequentially from the first page to the last (1, 2, 3.) in terms of what PDF viewers show. But if your source PDFs had printed page numbers as part of the content, a "Page 4 of 12" footer stamped on each page, those won't automatically update. They'll still say what they said in the originals. If you need consistent printed page numbers throughout the merged document, use the
Add Page Numbers tool after merging.
Yes. Each page keeps its own dimensions in the merged file. An A4 page will still be A4, and a US Letter page will still be Letter. If you need a uniform page size throughout the document, you'd need to convert the sizes first, most PDF readers can handle mixed-size documents fine, but some print setups don't like it.
The most common culprits are: the file is password-protected (unlock it first), the file is corrupted (try opening it in Adobe Reader or Preview to confirm), or the file is technically not a valid PDF despite having a .pdf extension. If you can open the file normally in a PDF reader and it looks fine, try uploading just that one file by itself to isolate the issue, sometimes a batch with one bad file stops the whole merge.