Use a PDF compressor tool
Reduce image resolution
Compress embedded images
Remove unnecessary pages
Delete unused objects and metadata
Save the PDF as optimized or reduced size
Convert images to grayscale if color is not needed
Lower scan quality when creating the PDF
Use a smaller font subset
Flatten annotations and form fields
Remove embedded fonts if possible
Export the file with web-optimized settings
Split large PDFs into smaller files
Recreate the PDF from the source file with lower quality settings