Reduce image resolution
Compress images
Convert images to JPEG instead of PNG where possible
Remove unnecessary images
Remove embedded fonts you do not need
Subset fonts
Delete unused pages
Remove annotations and comments
Flatten form fields
Flatten layers
Remove metadata
Optimize for web
Use PDF compression tools
Save as a lower-quality PDF
Convert color images to grayscale
Reduce page size
Remove duplicate objects
Re-export the PDF with smaller file settings
Use OCR only when necessary
Avoid embedding large attachments
Split large PDFs into smaller files