Compress images before adding them to the PDF
Reduce image resolution
Convert images to JPEG instead of PNG when possible
Remove unnecessary pages
Delete unused objects and metadata
Use a PDF optimizer or compressor tool
Save the PDF with a smaller file size setting
Flatten annotations, forms, and layers
Use font subsetting
Embed only the fonts that are needed
Convert scanned pages to grayscale
Lower the quality of embedded media
Remove bookmarks, comments, and attachments if not needed
Recreate the PDF from the source file with optimized settings
Split large PDFs into smaller files if appropriate