I'm also new to Illy and Photoshop, both of which are making me pull my hair out (much respect for graphic designers). I designed a simple letterhead with a horizontal bar that is supposed to go to the edge of letter size paper but when it actually prints, the bar doesn't extend to the edges. I have a bleed of .125 (1/8") set up so that I can extend this horizontal bar past the document edges so that when it prints, there are no funny edges. I'm printing at home on a non-commercial printer, an HP Color Laser Jet 5500 PCL 6. I've also made sure that the document is not scaled or "fit to page" before printing. And both printing directly from Illustrator and saving as PDF and printing produce the same result. Such a simple thing is driving me nuts.
I don't see on any specs I could find that your printer can print edge to edge. If it does not, what you are experiencing is the built in non-printable area. The only way to get edge to edge would be to print to larger paper than you design needs and trim it.
Take care, Mike
That would explain it then. Printing in itself is an area that I'll have to read more up on. Thanks Mike!