Choose the cover first, then add the appendix. Confirm that the list shows the cover above the appendix and that the total pages equal one plus the appendix page count. Merge once. The output should begin with the cover page followed by every appendix page in its existing order.
Read the exact run evidence
For a one-page cover and three-page appendix, the displayed result must say two source files and four output pages. Byte size depends on the actual inputs and fresh serialization, so use the displayed number rather than an estimate.
Inspect the downloaded PDF
Open the exact downloaded file in the reader used by its destination. Confirm the complete page sequence, page count, visible content, links, annotations, form behavior, accessibility, and any destination-specific requirements. Keep the sources: a successful page copy is not a certification that every PDF feature was preserved.
Understand the fresh document boundary
PDFMerge writes a fresh PDF containing copied visible pages. It does not promise preservation of document metadata, bookmarks, page labels, embedded files, portfolios, XFA, JavaScript, open actions, optional layers, tagged structure, PDF/A or PDF/X conformance, usage rights, encryption, incremental revisions, or digital signatures. A signature in a source does not sign the output.