Best option: Upgrade! PDF creation has been improved in both AC10 and AC11.
But to streamilne PDF creation, the best way to get percentage fills is to use a gray pen and a solid fill. Much smaller filesize, no scaling problems etc. Avoid bit-map patterned and percentage fills in combination with PDFs. (They are better in AC11, though.
AC4.1-AC26SWE; MacOS13.5.1; MP5,1+MBP16,1