This makes me think that the filter is only applied to images in the PDF. The Quartz Filter method didn't work for me, even when I applied a custom filter with aggressive settings. I had a PDF of handwritten annotations on a book exported from Goodnotes. This is for anyone who is in the same boat as I was. Adjusting the image size in terms of pixel count/resolution appropriate for the intended output medium might produce the biggest savings. If you created the PDF yourself then it would be obviously best to losslessly reduce the images before including them into the document (the PDF). The related muPDF is even available on the App Store. Ghostscript is available through a number of venues for macOS. Meaning: most of the time the savings gained might be very good, but sometimes the file size even increases. Those given here should not perform any lossy conversions or strip away important document structures. Gs -dBATCH -dNOPAUSE -q -sDEVICE=pdfwrite -dCompatibilityLevel=1.7 -dNOPAUSE -dQUIET -dPDFSETTINGS=/prepress -sOutputFile=Name_of_Outputfile.pdf To_Reduce_Input.pdf GhostScript with the following parameters:.Instead of Image Magick or Preview I suggest to try: Also: while you may not visually discern any quality loss, it is still a lossy procedure, but with less aggressive settings then the original Quartz-filter.) those PDFs with not much structure, without Bookmarks. (Although answer might well be worth a try for simple documents, e.g. Preview is very limited in its capabilities. Select your new filter when exporting file. Change compression setting, image size and add unique display name for your filter. The file should contain XML with new filter - you can base on the /System/Library/Filters/Reduce File Size.qfilter file or use my below example.Add there new filter file with unique filter - f.e.Create new directory (if you don't have it) - /Library/Filters.Thankfully, a custom filter can be added. The problem is - the default filter used during conversion has very low conversion settings.

Compress pdf file size in mac