Prepare the files
Download email and message attachments to a folder you can find in the file picker. Use clear names and avoid selecting duplicate versions. Shared links must first be saved as actual PDF files.
Check the sequence
Select at least two PDFs and use the list arrows to place them in reading order. Page order inside each original document stays unchanged. To include only a section, extract it before merging.
Keep the browser open and review the result
Changing apps, locking the screen or insufficient memory may interrupt processing. Try fewer files or use a computer if necessary. After downloading, check the page count and transitions. Keep signed originals: a merged copy does not preserve their verifiable digital signatures.