For a neighborhood meeting, you have an invitation, a three-page cost estimate, and two proposals in separate PDFs. Combining the files takes little time. The harder part is making sure the result contains every page once, keeps each proposal together, and does not place a blank scan in the middle of an explanation. Planning the sequence before combining is easier than repairing a long strip of similar-looking thumbnails afterward.
Decide what belongs in the packet
Put the source files in a working folder and open each one. Write a short intended sequence, such as invitation, estimate, proposal A, and proposal B, including each file's page count. Add those counts to establish an expected total. The total cannot prove that every page is correct, but it makes an omitted attachment or an accidental duplicate easier to notice.
Check whether one source already contains an attachment that is also available separately. Duplicate content does not always mean duplicate files. A proposal might be embedded after a cover letter and also supplied on its own. Resolve that overlap deliberately in your plan, rather than deleting pages from the finished packet because they look vaguely familiar.
Arrange files and pages separately
In a combining tool with previews, arrange whole files first, then expand individual pages only when necessary. Move a complete document as one unit whenever possible. If you move a single page, examine the pages immediately before and after its new position. A section should not suddenly begin with its third page.
Scans deserve extra care. Duplex scanning can produce blank backs, but an apparently empty page may contain a small note or the reverse of a stamped sheet. Rotate sideways pages before judging their reading order. Keep the original PDFs untouched and save the assembled packet with a new name so that an incorrect deletion remains easy to undo.
Read the finished file as a recipient
Reopen the saved output. Compare its page count and sequence with your plan, inspect the first and last page of every attachment, and read across the joins. Check links and bookmarks if readers will use them for navigation. Mixed paper sizes are not automatically wrong, but print scaling should not cut off important margins.
Do not confuse the page label displayed by a PDF viewer with a number printed on the page. Changing viewer labels does not replace visible page numbers. If the packet says “see page 8,” make clear which numbering system applies. For a short packet, referring to a clearly named attachment may be simpler than adding an entirely new numbering scheme.