Note the number it quotes. That is the real limit.
Use the recommended level and check the resulting size.
Cut by page range into two or three files and let the recipient merge them.
There are at least four different walls: an email attachment cap (commonly 20–25MB), a WeChat single-file cap, a portal upload cap (2MB, 5MB or 10MB are typical), and a cloud storage per-file limit. They differ enough that compressing blindly often wastes effort. Read the number in the error message.
Switch channel first — send a share link instead of an attachment. Split second — two smaller files that the recipient merges in seconds. Compress last, because it is the only option that permanently loses quality.
Either the file is still above the cap (some portals measure the size after unpacking), or the cap was never about size — it was about format, page count or editability. No amount of compression fixes those.
Sending as a file keeps the content intact, but a file over the cap simply cannot be sent. Sending as an image is what triggers recompression.
20–50MB for most providers, often lower for corporate mailboxes, and the recipient's limit applies too.
Not really — merging takes seconds with a local tool and the quality stays identical.