I use Excel 2010 with VBA.
I have the following code :
mySh.PageSetup.PaperSize = xlPaperLetter
mySh.ExportAsFixedFormat Type:=xlTypePDF, _
Filen
I use Excel 2010 and had this problem. I fixed it by changing the printer in Excel's dropdown list on the Print section of the File tab. My default printer is a Konica Minolta copy machine. I changed it to Local Printer (which doesn't actually exist) and it worked! I now have the VBA code returning an 8.5x11 PDF! Now I don't have to use our clunky old laptop with an old Office to get the right size.
Note that picking the Adobe PDF printer did not fix the problem. Just try messing with the different printer choices, or make a fake printer in your computer's Devices and Printers and use that. I hope it works for others with the same issue!