Merge PDF Files
Combine any number of PDFs into one. Drag the files into the order you want, take whole documents or just the pages you need from each, and see every page that will end up in the result, as a thumbnail, before you build anything. Everything happens in this browser tab.
- Nothing uploaded
- Works with no signal
- No sign up
- Quality unchanged
Nothing added yet.
What the merged file will contain
Add files to see the page order.
Click any page below to leave it out of the merge, and click it again to put it back. The colours and the tick show which document each page came from and whether it is going in.
Your PDFs never leave this device.They are opened and combined by your browser, the merged file is assembled here in the page, and the download comes from your own machine. Nothing is sent to a server, so nothing is stored on one. Open the network tab in your browser tools and merge something: there is no upload request to see.
Pages copied, never redrawn
The pages move across as objects rather than pictures, so text stays searchable and images keep the quality they had in the original files.
How to use this tool
Drop your PDFs onto the box at the top. Each one appears as a card showing how many pages it has, how large it is, and the size of its first page, all read straight out of the file.
Put them in the order you want by dragging a card onto another, or use the up and down buttons. If your files are already named sensibly, sort by name will usually do it in one click.
Every page of every document appears as a thumbnail in the order it will land in the result. Click one to leave it out and click it again to put it back, so you never have to describe a page choice in writing. The colour and the tick show which document a page came from and whether it is going in.
What the tool is working out
Before a single byte is copied, the tool builds a plan: a list of output pages, each one pointing at a specific page of a specific file. That plan is what the preview draws, so what you see is exactly what will be assembled. Hovering any page in it reveals a remove control, which is often faster than editing a range by hand, and it refuses to remove the last remaining page rather than produce an empty document.
Page choices are normalised on the way in. Duplicates collapse, so 5, 1, 3, 3 becomes pages 1, 3 and 5 in that order. A reversed range like 7-4 is read forwards. Anything past the end of a document is clamped, and a range that selects nothing marks the file as contributing nothing rather than quietly producing an empty stretch.
Blank separators, if you turn them on, go between documents only. Never before the first, never after the last, and never doubled up when a file in the middle turns out to be unusable.
Why merging does not lose quality
This surprises people who are used to image editors, where every save costs you something. Merging PDFs costs nothing, and it is worth understanding why, because the same reasoning tells you which PDF operations are safe and which are not.
A PDF page is not a picture. It is a list of drawing instructions: put this font at this position, stroke this path, place this image in this rectangle. Merging copies those instructions across along with the resources they reference. The output page contains the same instructions as the input page, so it renders identically forever. Nothing is decoded and re-encoded, so there is no generation loss to accumulate.
That is also why merged files are often smaller than the sum of their parts. Fonts and images live in a shared pool and pages point at them. Take three pages out of a two hundred page report and you carry over only the fonts and images those three pages actually use, not the other hundred and ninety seven pages worth.
The contrast is worth holding on to. Converting a PDF page to JPG and back does destroy quality, permanently, because the instructions are thrown away and replaced with a grid of pixels. Merging, splitting, rotating and reordering all stay in the instruction world and are lossless. Anything that rasterises is not.
A worked check you can repeat
Say you add three files: a two page cover letter, a ten page report, and a four page appendix. You leave the first blank, type 2-3 on the report, and type odd on the appendix.
The plan comes out as seven pages. Pages 1 and 2 are the cover letter. Pages 3 and 4 are pages 2 and 3 of the report. Pages 5 and 6 are pages 1 and 3 of the appendix, because odd on a four page document means 1 and 3. The map lists each one with its source.
Turn on blank separators and it becomes eight pages: the two blanks land after the cover letter and after the report extract, but not at the start or the end. Reverse the file order and the appendix comes first, its pages still in forward order, because reversing the file order does not reverse the pages inside each file.
The planning logic was checked against thirty five hand written cases and then fifteen thousand randomly generated ones, testing that output page numbers are always consecutive from one, that blanks never appear at either end or twice in a row, and that every output page points at a page that actually exists in its source file.
Mistakes that catch people out
Expecting reversed file order to reverse the pages. It reverses which document comes first. Pages inside each document stay in their normal order. If you want a document's pages backwards, that is a different operation.
Assuming the pages will all be the same size. They keep their originals, so mixing A4 portrait with A3 landscape gives you a document with both. That is usually what you want for a drawing set, and occasionally a surprise when printing.
Adding a password protected file. If it needs a password to open, it cannot be read, and the card will say so. The tool marks it as unopenable rather than silently dropping it, so a missing document does not go unnoticed.
Trusting alphabetical order for numbered files. Plain alphabetical puts page 10 before page 2. Sort by name here compares numbers properly, so 2 comes before 10, but check the order before you merge if the naming is unusual.
Merging when you meant to append. If only one document ends up contributing pages, the result is just a copy of it. The status line says so, because a merge of one is almost never what was intended.
Common questions
Are my PDFs uploaded to a server?
No. The files are opened and combined by your own browser, the merged document is assembled here on the page, and the download comes from your machine. Nothing crosses the network, so there is nothing on a server to store or delete.
Can I merge only some pages from each file?
Yes. Each file has its own thumbnails. Clicking a page is the only way to choose, so there is no syntax to learn. Leave it blank to take the whole document.
Does merging reduce the quality?
No. Pages are copied across as they are, with their text, vectors and images intact. Nothing is re-encoded or rasterised, so a merged page is identical to the page it came from.
Why is the merged file smaller than the files added together?
Because a PDF stores fonts and images once and references them. When you take a few pages from a large document, only the resources those pages actually use are carried over.
Can I merge a password protected PDF?
Only if it opens without a password. A file that needs a password to open cannot be read, and the tool will mark it as unopenable rather than silently skipping it.
Do the pages keep their original sizes?
Yes. Each page keeps its own dimensions and orientation, so mixing A4 portrait with A3 landscape produces a document with pages of both sizes rather than forcing everything to one size.
Related PDF tools and reference
Reference: ISO 32000, the standard that defines the PDF format this tool reads and writes.