Merge PDFs in the right order and catch missing pages

To combine a report and an appendix, put the source PDFs in the intended order, merge them, then open the downloaded file. Check three things: its total page count, the pages where one source ends and the next begins, and any pages whose content must be present. A correct count alone cannot prove that every page is in the right place.

Try a three-page merge

A small example makes the checks clear. In a recorded browser trial, part-a.pdf contained two pages marked ALPHA and BETA. part-b.pdf contained one page marked GAMMA. With A before B, the expected merged sequence was:

1. ALPHA
2. BETA
3. GAMMA

The actual iLovePDF download and PDF24 download each had three pages in that sequence. The first was 72,465 bytes and the second 69,006 bytes; the size difference does not rank their quality.

Before merging your own files, write down their page counts and the order you want. For a report followed by an appendix, the first appendix page should come immediately after the last report page.

Set the order in the browser

Open the iLovePDF Merge PDF page or PDF24’s Merge PDF page, and choose the source files. Check their displayed order before starting the merge. PDF24 documents dragging files to change that order, then merging and saving the result. Dragging was not part of the recorded trial, so check the displayed sequence after any move.

Download the merged PDF and open it. Do not rely on the names of the files you selected as proof of their final order. The order shown in the merge tool is the one to check before you merge; the downloaded pages are the result to check afterward.

If it helps you recognize the files, name copies 01-report.pdf and 02-appendix.pdf before selecting them. The prefixes are a reminder of your intended sequence, not a guarantee that a tool will arrange the files for you.

Check content as well as count

For the three-page example, a count of three is necessary but insufficient. Two separate PDF files were deliberately constructed locally from the same practice pages:

• The reversed file has GAMMA, ALPHA, BETA. All three pages are present, but the file order is wrong.
• The duplicate-page file has ALPHA, ALPHA, GAMMA. It still has three pages, but BETA is missing.

Open both deliberately incorrect practice files and compare them with the real downloads. Their three-page counts match, but their headings expose different mistakes. For the intended A-then-B merge, inspect all three pages and especially the join: BETA must be followed by GAMMA.

A two-page result when you expected three flags a missing page immediately. A three-page result still needs inspection because a duplicate can take the place of a missing page. Renaming the downloaded PDF cannot repair either problem; go back to the source files, correct the selection or order, and merge again.

Map a longer packet before merging

Suppose a packet has a one-page cover, a five-page report, and a four-page appendix. The expected total is 1 + 5 + 4 = 10 pages. A short page map gives you specific places to inspect:

Source copy	Source pages	Positions in merged PDF	Example first and last content
01-cover.pdf	1	1	Cover
02-report.pdf	5	2 to 6	Executive summary / Next steps
03-appendix.pdf	4	7 to 10	Item A / Item D

These headings and filenames are a hypothetical planning example. For a real packet, substitute words you can see on your own pages. Check the transitions from merged page 1 to 2 and 6 to 7, then locate the report’s “Next steps” and the appendix’s “Item D.” A source PDF’s printed “page 1” can appear at merged position 2 or 7, so use the merged viewer’s page position for this check.

If one appendix page is omitted, this example yields nine pages. If one page is duplicated while another is lost, the result can still total ten. Checking the source counts, joins, and distinctive content catches different mistakes.

Merge local copies with Python

The pypdf installation guide documents Python 3.9 or later and installation with pip install pypdf. Its merging guide shows how to append whole PDFs in sequence and write the result.

Download the two practice inputs into a folder you own. With Python installed, open a terminal there, run python -m pip install pypdf, then save and run this script:

from pypdf import PdfReader, PdfWriter

writer = PdfWriter()
for filename in ['part-a.pdf', 'part-b.pdf']:
    writer.append(filename)

writer.write('combined.pdf')

result = PdfReader('combined.pdf')
print(len(result.pages))
for index, page in enumerate(result.pages, start=1):
    print(index, page.extract_text())

The filename list sets the order: A, then B. A local October 7 check of this append-and-write procedure with pypdf 6.10.0 produced three pages containing ALPHA, BETA, GAMMA. The command prints each physical position and its extracted text, so you can check the sequence without relying on a completion message. Text extraction can help with pages containing text; inspect image-based or scanned pages visually.

Fix the problem you find

Wrong file order

Return to the selected inputs, put them in the intended sequence, and merge again. Rotating a page will not change where its source file sits in the packet.

Wrong page count

Compare the downloaded count with the sum of the source counts. Reopen the source PDFs and check that you selected every intended file. If the total is correct but content is wrong, look for a duplicate or substituted page.

A page looks unreadable

Open the corresponding source page at a comparable zoom before attributing the problem to the merge. File size alone is not a measure of visual quality.

A password prompt appears

Do not assume merging removes a source PDF’s password requirement. Resolve access to the source file before relying on a merged copy.

The Python example cannot find a file

Run it from the folder containing the two named inputs, or correct the filenames to match your copies.

If you need only some source pages, extract those pages before assembling the packet. If you need a continuous visible page-number sequence, add page numbers after assembly. For packets with interactive forms, bookmarks, or signatures, check those features in the finished file before using it; the page checks above do not establish their preservation.

Source note: The browser downloads are from September 29, 2026 and were parsed and rendered again on October 7. The reverse, duplicate and append-code outputs were constructed or checked locally on October 7; no new service upload was performed. All supplied practice content is synthetic. For your own files, choose a web upload only when it fits the documents’ privacy requirements.