Use a PDF compressor tool
Save the PDF as a reduced-size or optimized PDF
Lower image resolution before creating the PDF
Compress embedded images
Remove unnecessary pages
Delete unused objects and metadata
Flatten annotations and form fields
Convert scanned pages to black and white if possible
Use a smaller font subset
Reduce the quality of images and graphics
Export the PDF with web-optimized settings
Split large PDFs into smaller files
Recreate the PDF from source files with lower quality settings