How to merge PDFs here
Most of the time goes on getting the order right; the merge itself is quick.
- Add the files. PDFs and images can go in together, and files added later join the end. Try with sample files loads PDFs made for this site if you want to test the options first.
- Trim each file. Its Pages box takes a selection, so you can take the signature page of one document and chapters 2 and 3 of another without splitting anything first.
- Arrange. Every page of every file sits in one grid. Move a file up or down to keep its pages together, or drag a single page anywhere. Rotate, delete or duplicate a page, or insert a blank page after the selected one.
- Choose the options for bookmarks, forms, page size, page numbers, title and password, each explained below.
- Merge. A progress bar with a Cancel button shows how far it has got, and the finished PDF downloads as one file.
The page count, file count and estimated size update as you work. On the keyboard, the arrow keys move between pages, Alt with an arrow moves the selected page, R rotates it and Delete removes it. In our test, parts of six files merged into a 24-page PDF with 10 bookmarks in 0.2 seconds, and the file came to 74 KB.
What happens to your files: nothing is uploaded
Merging usually involves the most personal documents people have: a passport scan, bank statements and a payslip for a rental application, a medical letter with a claim form. None of them leaves your device. The first time you add a file, the page downloads its PDF engines (pdf.js from Mozilla to read pages, pdf-lib to write the new file); after that, reading, copying and writing all happen inside the tab, and the merged PDF goes straight to your downloads.
The check takes about 60 seconds. Open your browser’s developer tools (F12, or Cmd+Option+I on a Mac), choose the Network tab and clear it, then add your files and merge. You will see the engine’s code arriving from dothecalculation.com and the analytics and consent requests every page of the site makes, but no request the size of your files and none carrying their names, page counts or a password. For an airplane-mode test, add a sample file first so the engines are loaded, then disconnect and merge your real files. Our guide Are online PDF converters safe? explains what happens on sites that do upload, and how to test any of them.
Page order and page ranges
An empty Pages box means every page of that file. Otherwise, commas separate parts, and the order you type is the order you get:
- 1-3, 8 takes pages 1, 2 and 3, then page 8. 8- runs from page 8 to the end, and -3 takes the first three.
- last takes the final page, handy for a signature page when you do not know the page count.
- odd and even take every other page, useful when a scanner put a blank back after every page.
- 5-3 counts down through pages 5, 4 and 3, which fixes a document scanned last page first.
- 8, 1-7 moves page 8 to the front, such as a cover sheet that ended up at the back.
For whole files, Move up and Move down keep each file’s pages together. Sort by name uses natural order, so “scan 2” comes before “scan 10” instead of after it. Sort by date modified orders files by when they were last saved, which for an attachment is usually the moment it was downloaded, not the date on the document.
Merging a double-sided scan
A scanner with a sheet feeder but no duplex unit scans one side of the stack at a time: one pass gives a PDF of the fronts, you turn the stack over, and a second pass gives a PDF of the backs, in reverse, because the last sheet is now on top. The double-sided option collates them. Choose the fronts file and the backs file and the merge alternates a front, then its back. Backs are in reverse order is on by default because that is what turning a stack produces; switch it off if your scanning app already reversed them.
A worked example with a 6-sheet letter printed on both sides:
- The fronts file has 6 pages: the fronts of sheets 1 to 6, in order.
- The backs file has 6 pages, from the back of sheet 6 to the back of sheet 1.
- With Backs are in reverse order on, the result is 1 front, 1 back, 2 front, 2 back and so on to 6 back: 12 pages in reading order.
Then go through the grid page by page. A blank back can be deleted, or kept if the letter will be printed double-sided again. If the stack was turned top to bottom rather than left to right, every back is upside down: press R twice on each to turn it 180 degrees. A sheet that jammed and was rescanned on its own can be added as a separate file and dragged into place.
Forms, signatures and annotations
Most of a page comes across unchanged: text stays selectable and searchable, images are copied without being compressed again, and comments and highlights travel with their pages. Links from one page to another inside the same source file are re-pointed to that page’s new position; links to pages you left out are removed and counted in the result. Links to websites are kept.
Form fields are the exception. A field’s value belongs to a form that covers the whole document, not to its page, so it cannot be copied with some of the pages. Flatten, the default, draws each field’s current value onto the page: it stays visible and prints, but can no longer be edited. Remove fields deletes the fields and their values, which suits a blank form kept only for reference. The result says how many fields were flattened.
A digital signature is a cryptographic seal over the exact bytes of the signed file. Copying its pages into a new file produces a document the signature does not cover, so the merged copy can at most show what the signature looked like, with nothing a reader can verify. When a file contains a signature field, the tool explains this and asks you to tick I understand before continuing.
The better route is to keep the signed original untouched and send it alongside the merged bundle as its own file. If you are arranging the signing yourself, merge first and have the finished bundle signed last.
Page sizes and orientation
Keep as is, the default, leaves every page at its own size and orientation, so an A4 letter, a US Letter contract and a landscape spreadsheet can sit in one file and each reads correctly on screen.
Printing is where mixed sizes bite. US Letter is about 6 mm wider and 18 mm shorter than A4. Printed at 100% on A4 paper, a Letter page loses a thin strip at the sides; an A4 page on Letter paper loses around 18 mm of its length. Print dialogs set to fit the paper avoid the clipping, but then each page prints at a slightly different scale.
Scale to A4 or Scale to US Letter resizes every page to that paper, keeping its shape and orientation, centred, with annotations scaled along with it. A Letter page going onto A4 shrinks to about 97% to fit the narrower width; a landscape page stays landscape. After that, printing at 100% puts every page on the paper as it looks on screen. Do not scale a drawing made to scale, such as a floor plan, because its measurements will no longer match a ruler.
A blank page inserted in the grid takes the size of its neighbour, so a blank used to start the next document on a fresh sheet matches the pages around it.
Adding images and phone scans
JPG, PNG, WebP, GIF, BMP, SVG, HEIC and HEIF from an iPhone, and AVIF where your browser can decode it, can all go into the same merge as PDFs. Each image becomes a page through the converter behind our JPG to PDF tool: placed on A4 (US Letter if your browser is set to the United States or Canada) within a small margin. JPG photos go in without being compressed again, and photo metadata such as location is removed. That covers the everyday jobs: an application form followed by photos of the supporting documents, or an expense claim with its receipt pictures after it.
For more control, such as pages that fit each image with no border, wider margins or smaller phone photos, convert the images in the JPG to PDF tool first and add that PDF here.
File size after merging
The size estimate multiplies each source’s size by the share of its pages you are using, so half the pages of a 4 MB file count as 2 MB. For scans, where each page is its own picture, that is close. For documents exported from Word or accounting software it often runs low.
The reason is shared material. A PDF stores its fonts, and often a logo, once for all its pages, so a single page taken from a long report still brings the report’s fonts with it. Each source also brings its own copies: twelve monthly statements from one bank merge into a file holding twelve copies of the same logo and twelve sets of the same fonts.
Our Compress PDF tool removes most of that. Its lossless clean-up keeps one copy of any object whose contents are identical; in our test, a 40-page PDF with the same logo stored 40 times went from 402 KB to 28 KB. Fonts cut down to different sets of letters in each source are not identical, so those copies stay. Our guide on how to reduce PDF file size explains where the rest of the bytes go.
Password-protected files, and protecting the result
When you add a PDF that needs a password to open, the page asks for it beside the file, and once it is right the file’s pages join the grid. The password is held in this tab’s memory only, never saved or sent.
If any input was protected, Protect with password switches itself on, because otherwise the merged file would open for anyone. Type a password and the merged PDF is encrypted with AES-256; switch the option off only if you have decided it does not need one. You can also turn it on for any merge, such as a bundle of identity documents going by email. Send the password by a different route from the file.
Some PDFs open freely but carry restrictions set by their author. If a file forbids assembling its pages into another document, the tool does not merge it and says why: ask the sender for a copy without the restriction. The tool never removes passwords or restrictions from files you cannot open, and this site has no PDF unlocking tool.
Your data
Your files stay in this tab’s memory until you remove them or close the tab. No record is kept of their names, contents or page counts, or of the title you give the merged file. Only your settings, such as the bookmark and page-size choices, are saved in your browser’s local storage, and clearing this site’s data removes them. Passwords are never stored.
General information about merging PDF files. Check the merged PDF page by page before sending anything official: order, blank pages, flattened form values and scaling. Merging invalidates digital signatures, so send signed originals separately. This is not legal advice about which documents an office or court will accept.