Open the PDF in Preview
Click File
Click Export
Choose Quartz Filter
Select Reduce File Size
Save the new PDF
Use Adobe Acrobat’s Compress PDF tool
Use online PDF compressors if needed
Remove unnecessary pages before saving
Lower image resolution before creating the PDF
Convert images to grayscale if color is not required
Save as a smaller PDF from the original app
Use Print and choose Save as PDF with reduced settings
Optimize PDF in Acrobat if available
Split large PDFs into smaller files
Flatten annotations and form fields if supported