How to Merge PDFs

You've got a flight invoice, two taxi receipts, a hotel folio, and a coffee chit — and finance wants one PDF, in order, by Friday. Or you've scanned a book one chapter at a time and need them welded into a single file. Or you're assembling a portfolio from three different design tools and a Word brief. The answer is the same: merge the PDFs. This guide walks through the cleanest way to do it in your browser with Flint's Merge PDF tool, plus the things people tend to get wrong.

Why merge PDFs in the first place?

Merging sounds trivial. It isn't — the reason it matters is that the world wants one file, not five. Anywhere a document gets reviewed, filed, signed, or archived, splitting it across multiple PDFs creates friction. A single tidy file is easier to email, easier to print, easier to find again later, and far easier to sign as a package.

The cases people actually merge for:

Expense reports. Invoice, receipts, taxi chits, hotel folio — finance wants them all together, in the order they happened, with a cover sheet at the front.
Books and long documents. Scanning a book chapter by chapter, or a thick report section by section, is much faster than scanning the lot in one go. Merge afterwards and you get one continuous file.
Portfolios and submissions. Cover letter, CV, work samples, references. Hiring portals almost always want a single PDF; this is how you produce it.
Contract bundles. Main agreement, schedules, annexes, signature page — stitched together so the recipient sees the whole thing in the right order.

How to merge PDFs in Flint

Open the Merge PDF tool, drop your files in, drag them into the order you want, hit merge. That's the whole flow. In a touch more detail:

Drop in every PDF you want to combine

Drag your files onto the upload card or pick them from your computer. There's no fixed limit on how many you can add; people routinely merge a dozen or two. Each file appears as a card with its filename, page count, and a thumbnail of the first page so you can recognise it at a glance. Pro accepts files up to 250 MB each.

Drag the cards into the order you want

This is the step most people rush. Grab any card by its handle and drop it where it should sit. Want the cover letter first, then the CV, then work samples? Reorder the cards to match. Need to remove a file you added by accident? There's a small remove button on every card. Take ten seconds here and save yourself re-merging later.

Hit merge and the combined PDF opens in the editor

Flint stitches them together server-side — pages aren't rasterised or re-rendered, so text stays selectable and any embedded fonts come along untouched. The merged file lands in the Flint editor where you can do anything else: reorder pages, sign, annotate, redact, or just hit download.

What to do once the PDFs are merged

The merged file lands directly inside the Flint editor, so the natural follow-ons are one click away:

Pages still out of order? Open Reorder PDF Pages for a thumbnail view where you can drag individual pages around — useful when the file-level order was right but a page or two inside one of the inputs was off.
Need to drop a few pages? Delete PDF Pages lets you multi-select and remove blanks, scrap pages, or internal cover sheets you no longer need.
File too heavy to email? Run Compress PDF — merged files with lots of scanned pages compress especially well. There's a full walkthrough in our compress-a-PDF guide if you want the detail.
Sending for signature? Use Sign PDF on the merged bundle so the whole package gets signed together — the electronic signing guide covers the request-from-someone-else flow.
Tidying it up? Edit PDF for text and image tweaks, Annotate PDF for highlights and comments.

Other ways to merge (and when they make sense)

Flint isn't the only way to glue PDFs together. Each path has a moment where it's the right choice.

Preview (macOS)

Open the first PDF in Preview, show the sidebar, then drag other PDFs onto the sidebar to append. Save As to a new file. Fast for two or three files on a Mac you're sitting at; clumsy beyond that, and useless on Windows or anything without Preview installed.

Adobe Acrobat

Combine Files is buried in the Tools panel; once found, it works well. The catch is that Acrobat is a paid desktop install and the workflow is slower than dragging files into a browser page.

Command line (pdftk, qpdf, ghostscript)

Scriptable, free, fiddly. Good if you're merging the same set of files on a schedule from a server. Terrible if you're a human with five PDFs in a Downloads folder.

Flint (the case for it)

Browser-based, so it works on the laptop you've borrowed from a colleague as well as your own. Drag-to-reorder is built into the merge step itself, which is the thing most desktop apps make harder than it should be. And once the merged file exists, everything else you might want to do to it lives on the same site — no exporting, re-importing, switching tools.

Tips for a clean merge

Rename your files before uploading. 01-cover.pdf, 02-cv.pdf, 03-samples.pdf sorts itself alphabetically and gives you the right order from the off. You can still drag, but you won't have to.
Check the page count after merging. Add up the pages of the inputs in your head; the output should match. If it doesn't, something went wrong — usually a file failed to upload and the merge proceeded without it.
Don't merge before you sign. If the recipient is signing multiple documents, merge first, send the bundle once. Signing each separately and merging afterwards leaves the signed pages intact but breaks the signature audit trail's view of the package.
For very large stacks, merge in batches. If you've got fifty files, merge them in groups of ten, then merge the groups. Easier to spot ordering mistakes and faster to recover from.

Merge PDF: frequently asked questions

Does the order I drop files in matter?

Yes — the order on the merge screen is the order in the final PDF. Drag the cards around before hitting merge if it's not what you want. You can also reorder individual pages afterwards in Reorder PDF Pages.

How many PDFs can I merge at once?

There's no hard cap. Twenty-plus is common; we've seen people merge hundreds. Each file can be up to 250 MB on Pro.

Does merging change the content of the pages?

No. Pages are stitched, not re-rendered. Text remains selectable, fonts stay embedded, vector graphics stay sharp, and any form fields or annotations carry across.

Are my files private?

Yes. Uploaded files land in your private Flint library, the merge happens against your account, and the result is yours alone. Delete anything anytime from My Documents. We don't share, sell, or train on the files.

Can I merge PDFs with other file types — Word, images?

Convert them to PDF first, then merge. Use Word to PDF for documents and JPG to PDF for images, then drop everything into Merge.

What about the reverse — splitting one PDF into many?

That's Split PDF. You can carve out a page range, split a long document into equal chunks, or pull out individual pages.

Ready to merge?

Drag your files into Flint's Merge PDF tool, get the order right, and you'll have one combined file in seconds. Everything else — signing, compressing, deleting pages, sending — lives right next door.