Open the PDF in Preview
Click File
Click Export
Choose Quartz Filter
Select Reduce File Size
Save the smaller PDF
Use Adobe Acrobat’s Compress PDF tool
Use online PDF compressors
Print the PDF to a new PDF with lower quality
Reduce image resolution before saving
Remove unnecessary pages or attachments
Flatten annotations and form fields
Save as optimized PDF if available
Recreate the PDF with smaller image settings
Use a PDF editor to compress embedded fonts and images