Put your documents together into one

A PDF (Portable Document Format) is a type of file that looks the same on every computer, phone and printer. That's why councils, banks and other organisations usually ask for documents as PDFs. File names end in .pdf.

You may see this job called "merge PDF", "combine PDF files" or "join PDFs" on other websites. They all mean the same thing: taking several documents and putting their pages, one after another, into a single PDF. "Merge" just means "join together".

When you add a PDF, this page opens it to count its pages and draw a small picture of the first one. When you press Save, it copies every page of each document, exactly as it is, into a new PDF in the order you've chosen. It doesn't change the writing inside your documents, and it can't edit them: it only puts them together. Sideways pages stay sideways, just as they were.

Photos are a little different, because a photo isn't a page yet. Each photo is placed on its own A4 page with a small white border, the same as a printed letter. Photos from modern phones are very detailed, often 3 to 5 megabytes (MB) each, so each one is shrunk to a sensible size (about 2,000 dots across) first. The writing stays clear, and the file is much smaller. Phones also save which way up you were holding them, alongside the picture. This page reads that and turns the photos automatically, but you can always turn one yourself with the "Turn" button.

Before you save, the page quietly makes the joined document so it can tell you exactly how many pages it will have and how big the file will be. Many websites only accept files under 2 MB or 5 MB, so it's worth knowing before you try to send it.

Page numbers, a contents page and labels. If you've searched for how to "add page numbers to a PDF" or make a "contents page", this is that job. A set of documents put together for someone to look through, with page numbers and a list of what's inside, is sometimes called an "evidence bundle" (courts and tribunals often use that word). When you tick the extras, the page writes the numbers and labels on top of each page, in a small white box near the edge, so they cover as little as possible. It checks which way up each page is meant to be seen, so the numbers come out the right way up on sideways pages too. The contents page counts as page 1, so the page numbers in the contents list match the numbers at the bottom of each page.

The writing in the extras uses a font (a style of lettering) called Liberation Sans, which is built into the file. Some simpler fonts can't show Welsh letters like ŵ, ŷ and â, so we picked one that can. Long headings are made a little smaller, then split over more lines, so they always fit. The extras only tidy the layout: the page can't read your documents, so it can't tell whether they're the right ones, and nothing here is legal advice.

A few things this tool can't do. Some PDFs are locked with a password, or locked so they can't be changed. It can't open those. That's the lock doing its job, not a fault. If a document has boxes you can type into (a form), what's written in them is kept, but the boxes may not stay typeable in the joined copy, so fill them in before joining. Word documents need saving as a PDF first (in Word: File → Save As → PDF). iPhone photos in the newer HEIC format can't be opened here yet.

All of this happens inside your web browser (the program you're using to view this page, such as Chrome, Edge or Safari), using two free, open-source helpers called pdf-lib and PDF.js that are kept on our own website. Your documents are never sent anywhere.