Compress images
Enable the CompressImages property and assign the ImageQuality provided in the PdfCompressionOptions class to compress every picture in a PDF file.
Optimize embedded fonts
Activate the OptimizeFont property to improve the embedded fonts in an existing PDF file. Using this method, all the unnecessary glyph data is removed, reducing the font file size.
Remove metadata
Enable the RemoveMetadata property to remove metadata to shrink the PDF's size.
Optimize page content
By optimizing the page's contents, all uncompressed text will be compressed and all unneeded commented lines, white spaces, and end-of-line characters will be converted to spaces.
Compress the PDF content
Using the PdfCompressionLevel enum, you choose the compression level for the document. Compression levels like best, normal, none, etcand others can be set.