I went to Hallmark and got some printable graduation invitations. The lady there said she used them and it was really easy. Well...not so much. My dad's laser jet printer was unable to print them, as was my hp printer (that supposedly is able to print these, but it doesn't). They are thicker than paper and the size of a letter/card (think of a Hallmark card, that's the same thickness and size). What is the best printer I could use and where could I find one? Thank you!