Print to PDF to reduce file size always tabloid not custom

I have a pdf portfolio that I want to reduce in file size by printing to pdf again in acrobat with using "smallest file size" in the advanced tab found at the top of the printing menu. There's about 5 different places to pick page size with no sense of what option takes priority. I changed them all to my custom page size - even the one in "smallest file size" settings... The pages still print tabloid even though I want them 17 x 8.5. Is there a sixth page size option I'm not aware of that supercedes all the others? Thanks