how reduce the size of a pdf file

I often use I Love PDF. It's free and very quick and easy (there is a limit to how many you can do per day, and a maximum size, but a one-off 65MB file will be no problem). I Love PDF - compress PDF

FWIW, Adobe has free online PDF compression.

https://www.adobe.com/acrobat/online/compress-pdf.html

Don't forget that Apple's Mail Drop is at your disposal with iCloud email. This is an alternative to sending a large file. Mail uploads the file (up to 5GB in size) to your iCloud account and provides your recipient with a link to download the "attachment" in full size. See Apple's instructions in Send large attachments in Mail on Mac - Apple Support.

Just to add, I compressed a 23.4 MB file to 2 MB at the highest compression level. There are three levels.

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