Merge PDF
This PDF merger puts two or more files into one PDF, in the order you upload them. Each file can be up to 25 MB. Pages are copied as they are, not compressed again.
merge-cover.pdf (1,086 bytes, 2 pages) then merge-exhibit.pdf (873 bytes, 1 page) → 1792694079182-merged.pdf (1,308 bytes, 3 pages, 41 ms)
Processing: processed on our servers, then deleted — no watermark, no account required for everyday jobs
About Merge PDF
This PDF merger puts two or more files into one PDF, in the order you upload them. Each file can be up to 25 MB. Pages are copied as they are, not compressed again.
Worked example
The measured run added merge-cover.pdf first and merge-exhibit.pdf second, then pressed Run Merge PDF. The cover file was 1,086 bytes and two pages, labeled Cover — invoice packet and Terms — page two. The exhibit was 873 bytes and one page, labeled Exhibit A — photo log. The download was 1792694079182-merged.pdf, 1,308 bytes and three pages. Those three labels stayed in that order. The copy finished in 41 ms. File sizes went up because a new PDF wrapper was written around the same pages, not because the pages were rebuilt.
When it fails or surprises you
protected.pdf is 1,251 bytes and opens only with the password secret123. Merge stops with this text: Input document to `PDFDocument.load` is encrypted. You can use `PDFDocument.load(..., { ignoreEncryption: true })` if you wish to load the document anyways. empty.pdf is 0 bytes and shows: Failed to parse PDF document (line:0 col:0 offset=0): No PDF header found. corrupt.pdf is the nine bytes not a pdf and shows: Failed to parse PDF document (line:0 col:18 offset=9): No PDF header found. One file never reaches the server from the button: it reads Add 1 more file. A direct one-file request returns At least 2 PDF files are required to merge. A 27,262,976-byte upload, past 25 MB, shows Internal server error.
What a PDF file merger will not do
There is no drag handle, so you cannot reshuffle the list after the files are added. Every page of each file is copied. People use this page to merge PDF files when a portal wants one attachment. The job will not interleave them, stamp page numbers, or build bookmarks across the originals. It will not accept Word, JPG, or Excel. Calling this a PDF compiler would oversell it: the pages are copied, not laid out again. Next step when the packet is too long: /tool/split-pdf. Next step when you hoped the merge would shrink photos: /tool/compress-pdf, which also leaves embedded images alone.
How to use
- 1
Add the PDFs in reading order. The label shows (2 required) until two files are selected.
- 2
Press Run Merge PDF. With one file the same button reads Add 1 more file and does not start.
- 3
Press Download file. The saved name ends in merged.pdf. Check the first pages before you send it.
Privacy
Merge PDF uploads the files you chose, writes one PDF, and deletes the temporary copies after the download.
Frequently asked questions
Why does the button say Add 1 more file?
Merge requires two PDFs. With one file selected the button reads Add 1 more file and stays disabled. The line above the list also shows (2 required). A one-file request that bypasses the button gets At least 2 PDF files are required to merge.
Will a password-protected PDF merge?
No. protected.pdf failed before any page was copied. The on-screen text names PDFDocument.load and says the input document is encrypted. Unlock it on /tool/unlock-pdf when you know the password, then merge the unlocked file.
Does this PDF merger recompress images?
No. The measured merge of a 1,086-byte file and an 873-byte file produced 1,308 bytes in 41 ms by copying pages. Photos inside a source PDF stay at their original encoding.
What do a 0-byte file and a corrupt file show?
empty.pdf shows Failed to parse PDF document (line:0 col:0 offset=0): No PDF header found. corrupt.pdf, whose contents are the letters not a pdf, shows the same kind of message with offset=9.
What happens above 25 MB?
A 27,262,976-byte upload is rejected by the 25 MB limit. The page does not show a friendly size message. It shows Internal server error.
Multi-step workflows
Merge and Compress PDF Online
Combine multiple PDFs into one file, then shrink it for Gmail and Outlook — free step-by-step workflow on FileToolsHub.
Compress PDF for Email
Reduce PDF file size for Gmail, Outlook, and portal uploads — when to compress, when to split, and free tools on FileToolsHub.
Protect PDF Before Sharing
Add a password, compress for email, and finish client PDFs safely — free workflow on FileToolsHub.
Related guides
PDF Online vs Desktop Apps for Quick Edits
When a free browser PDF tool on FileToolsHub is enough — and when you still need Acrobat or a desktop suite. Clear privacy and workflow comparison.
Compress a PDF for Email (and When Splitting Is Smarter)
Gmail and Outlook reject oversized PDFs. Here’s how to shrink scans and packets — and when to split or merge instead.
Protect a PDF Before You Send It to a Client
A short checklist: finalize the packet, compress if needed, watermark when useful, then password-protect — and share the password separately.
How to Merge PDFs Online for Free
Combine invoices, contracts, or scans into one PDF in your browser — no Acrobat install, no watermark for everyday jobs.