Join a stack of PDFs into one document

Six files, one board pack, due Thursday

Dana runs the office for a small charity. By 5 pm on Thursday the trustees expect one board pack in their inbox, and she has six pieces from four people: a 2-page agenda, 4 pages of minutes from the last meeting, an 11-page finance report exported from the accounting software, a 3-page update from the director, and two supplier quotes that were scanned at the front desk, one page each. One of the quotes came from a US supplier on Letter paper; everything else is A4.

That is 22 pages that need to read as a single document, in agenda order, without anyone printing six attachments. The rest of this page follows her stack, but the same method works for a tender submission, a grant application or a course reader.

Get the stack ready before you open the tool

Five minutes of preparation saves a second run. Go through this list first:

• Collect every part as a PDF. A Word file or a phone photo is not a PDF yet; convert it first (photos go through Images to PDF).
• Write the running order on paper or in a note: agenda, minutes, finance report, director's update, quote A, quote B.
• Trim parts that carry pages you do not want to send. The merge takes each file whole, so a 40-page bank statement stays 40 pages unless you remove pages first.
• Open anything with a password. A locked file is turned away; make an unlocked copy with Unlock PDF using the password you already have.
• Keep a copy of any signed original. The merged file cannot carry a valid digital signature (more on that below).

Merging the stack in PDFGym

1. Open Merge PDF and press Choose PDFs, or drop the files onto the page. You can add them in several batches; each new file joins the bottom of the list.
2. Read the list. Each row shows the file name and its page count, and the totals underneath should say 6 files and 22 pages for Dana's pack. A wrong count means a wrong file.
3. Fix the sequence with the up and down arrows beside each row. The cross removes a file you added by mistake. The list from top to bottom is the page order of the result.
4. Look for a note under any file name. It names what that file holds that will not survive, such as bookmarks or interactive form fields.
5. Press Merge PDFs. The progress view walks through reading the originals, copying pages in your order, writing the new file and checking every merged page.
6. Press Download. The file is named after the top entry plus "-merged", so Dana gets agenda-merged.pdf and renames it to board-pack-march.pdf before sending.

What each part of a source file becomes

The tool copies pages into a brand new document. Anything stored at document level, rather than on a page, is left out. This is the full picture:

For Dana, the useful follow-up is page numbers: six sources means six separate numbering schemes. Stamp PDF can number all 22 pages in one pass after the merge, so trustees can say "page 14" in the meeting and mean the same page.

How the result is checked before download

Before copying anything, the tool reads every source page and records three facts about it: the selectable text, the width and the height. After writing the new file it opens that file again and reads it the same way. The page total must equal the sum of the inputs, each page's text must match its source, and every page must keep its dimensions.

If any of those comparisons fails, you get an error instead of a Download button. A pack that quietly lost page 9 of the finance report is the outcome nobody notices until a trustee asks about it, so the tool would rather give you nothing. The check cannot judge order, though. Putting quote B before quote A is a valid merge; only you know it is wrong.

Errors that slip through, and the fix for each

Trusting the file picker's sort. Files arrive in the list in the order the picker hands them over, often alphabetical. "Quote-B.pdf" lands above "minutes.pdf" and "part-10" lands above "part-2". Fix the order in the list, not by renaming.

One part sent as the wrong version. The director emails a corrected update at 4 pm. Rather than rebuilding, open the merged pack in Organize pages, delete the old three pages, then merge the new file onto the end and drag its pages back into place.

A pack too big for the mail server. Merging adds sizes together and never shrinks them; scanned pages make it worse. Compress the finished file once, as described in the merge-then-compress guide.

Skipping the read-through. Open the result and look at the first page of every part. Six glances are enough to spot a reversed pair.

Times a browser tool is not the right route

Sometimes the honest answer is a different tool or no merge at all.

If a part carries a digital signature that the recipient must be able to verify, keep that file as it is. A signature covers one exact file, and a merged copy is a new file. Send the signed contract alongside the pack instead of inside it.

If readers need clickable bookmarks to move around a long document, such as a 300-page tender response, use a desktop PDF editor that can rebuild an outline after combining. On a Mac, Preview can also combine files offline: open the first one, show thumbnails from the View menu and drag the other PDFs into the sidebar. Windows has no built-in way to do it.

If your organisation only allows approved software for client documents, ask IT first, even though nothing here is uploaded. And if the recipient's system files each document against a separate record, as many accounts departments do, one combined file just makes their work harder. Ask before you merge.