Which PDF tool do I need?
Start from the problem. A file that is too big to send needs Compress PDF. Several files that should arrive as one need Merge PDF. One long file that should be several, or only a few of its pages, needs Split PDF. Pages that are sideways, upside down or out of order need Organize PDF. Photos that must become a document need JPG to PDF, and pages that must become pictures need PDF to JPG.
For the most common compression jobs there are pages with the target already set: under 1 MB for strict forms, a 10 MB start for email attachments, and Recommended for scanned paper documents.