HP LaserJet 4 Plus not printing all emails

[CardPuller]

In a small office we have two printers - a HP LaserJet 4000 with 8MBs and a HP LaserJet 4 Plus with 2MBs. The LaserJet 4 Plus will not print all emails (ones with extra formatting like order receipts with boxes, etc.) The HP 4000 prints them all fine. I have the latest drivers installed for each printer. I am assuming that this is due to the lack of memory in the HP 4 Plus. Can anyone confim this before I order more RAM? Thanks.