Use a PDF compressor tool
Reduce image resolution
Compress images before adding them to the PDF
Convert images to JPEG instead of PNG when possible
Remove unnecessary pages
Delete unused objects and metadata
Flatten annotations and form fields
Embed only required fonts
Subset embedded fonts
Lower scan quality for scanned documents
Save the PDF as an optimized version
Remove bookmarks, comments, and hidden layers
Use grayscale instead of color when acceptable
Convert large graphics to simpler formats
Recreate the PDF with smaller source files