Jun 24, 2020 Now, you can reduce the size of this newly created PDF file. First off, select a PDF file you want to compress on your Mac. Next, double-click on that PDF file; you will see a Preview on your Mac. This is a default feature on your Mac; in case, Preview doesn’t open, you need to try again.
Reduce Mac Mail App Size Dimensions
Mail User Guide
Here are suggestions to try if mailboxes are so big you can’t find messages, or you want to reduce the amount of storage space that Mail uses on your Mac.
Mac Mail App Update
In the Mail app on your Mac, do any of the following:
Delete messages you don’t need anymore, especially those with large attachments.
Save attachments to your Mac, then delete the attachments from messages.
Create more mailboxes to organize your messages. For example, if you have messages related to travel plans, you could create a mailbox called Travel and move travel-related messages to that mailbox.
Use rules to automatically move incoming messages from your Inbox to other mailboxes. For example, you could create a rule to move travel-related messages to the Travel mailbox as they arrive. You can also use rules to process messages already in mailboxes.
