I work on Lexmark laser printers and from the look of that paper it could be the toner cartridge but my guess is the fuser. It looks like the toner isn't adhering to the paper which would be a bad fuser and also when they start jamming under the fuser it means it's going bad. But then again I haven't worked on a HP one.

I'm having printer problems myself tonight. My kitten decided to play with the paper as it was feeding out and jammed it good. I love my kitten