PDF4 min readUpdated March 2026

How to merge PDFs without installing software

Combining PDFs used to mean opening Acrobat or hunting for a decent free app. Now you can do it in your browser in about ten seconds, without handing your documents to anyone.

Why merging PDFs is still annoying in 2026

Adobe Acrobat is the obvious tool for PDF work, but it costs $25 a month. The free version of Acrobat Reader doesn't let you edit or merge files at all. macOS Preview can merge PDFs, but the process is unintuitive (you drag pages in the thumbnail sidebar and save a copy, which trips people up every single time). Windows has no built-in PDF merge tool.

Most people end up on SmallPDF or ILovePDF, which work fine but upload your documents to their servers. For invoices, contracts, or anything confidential, that's worth thinking about.

Browser-based PDF merging: how it works

Browser-based PDF tools use a JavaScript library called pdf-lib to parse and reconstruct PDF files directly in the browser tab. You load the files from your device, the library reads their page data, assembles them in the order you specify, and generates a new PDF in memory. The combined file is downloaded directly to your device.

No upload happens at any point. The files never leave your machine.

I use this regularly when combining monthly invoices into a single document for accounting. It's faster than opening Preview and the files stay on my laptop the whole time.

How pdf-lib handles this

pdf-lib reads each PDF's page data, fonts, and embedded resources, then writes a new PDF containing all of them in sequence. It can even deduplicate shared resources (like fonts used in multiple files), which sometimes reduces the final file size below what you'd expect.

Comparing your options

Method	Cost	Files go to a server	Setup required
Filagram (browser-based)	Free	No	None
Adobe Acrobat Pro	$25/month	Yes (cloud sync)	Install + account
SmallPDF / ILovePDF	Free (limited)	Yes	Account for more features
macOS Preview	Free	No	Mac only, fiddly UI
PDF24 / PDFsam	Free	Depends on version	App install

When to use each option

For most people who occasionally need to combine PDFs, a browser-based tool is the right choice. No install, no account, nothing leaves your device. It handles the common cases: combining invoices, merging scanned documents, assembling a report from separate sections.

Adobe Acrobat Pro makes sense if you're doing heavy PDF editing daily: adding signatures, editing text, OCR scanning, form creation. For just merging, the monthly cost doesn't make sense.

The server-based online tools (SmallPDF, ILovePDF) work well for non-sensitive documents where you don't mind the upload. Their interfaces are polished and they handle large files reliably. If privacy matters, use a browser-based option.

PDFsam Basic is a decent free desktop app if you need page-level control, like merging specific page ranges or interleaving pages from two documents. The UI is less approachable but it's powerful.

Things to watch out for when merging PDFs

Before you hit merge

Check the page order. Most tools let you drag and reorder files before merging. Check it before downloading.
Unlock password-protected PDFs first. Browser-based tools can't process an encrypted PDF without the password.
Large files are slower in the browser. PDFs over 50 MB each may take a while depending on your device. For very large files, PDFsam may be faster.
Final size = combined inputs. The merged PDF will be roughly the sum of all input file sizes (minus any resources pdf-lib can deduplicate).

One thing to know about macOS Preview

When merging in Preview, you need to use “File > Export as PDF” and not just Save. If you just save, you may overwrite one of your original files. I've seen this catch people out more than once.

How to merge PDFs using Filagram

Open the merge tool below. Drop two or more PDF files into the upload area. Drag to reorder them if needed. Click merge, and download the combined PDF. The whole thing takes under a minute for most documents.