Ahh, this is so true. I used to be a printer by trade, and believe me., I learned more about paper than I ever wanted to.

Where you aware that paper has a grain? Cut a large square sheet and hold it by your fingertips in the center. Now turn the paper 90 degrees and do it again. One way will flex more than the other. Paper will feed through a press and printer better if it's with the grain. This is not an issue usually with 8.5x11 as the parent sheets can be cut evenly with the paper all facing the same direction. Parent sheets are usually 23 by 35 inches.This allows for 8 sets of paper cut with VERY little waste. 8.5 x 14, on the other hand, will only allow four sets cut with the grain and one set cut against the grain. This means that 20% of the legal paper you feed through the printer will curl more than the other 80%. This can be a HUGE difference in terms of how paper will feed through a press. I have, as much as I hate to admit it, thrown away over 400 sheets of legal at a time (when I say threw away, I mean made into non-printed material, like note pads and such). It simply wasn't worth my time to try and force it through the press. I spent more time cleaning out the press than I did actually printing. It became a cost saving deal.

Inks are something else people are rarely aware of. Blue is much more difficult to run than red as the blue is a much lighter ink. The tolerances for a good run are FAR narrower for blues. the only thing worse is gold ink. Royal PITA.

Also, when working with non-metal plates (most of the time for runs less than 20,000) your results will be MUCH better if your original was printed at around 300-450 DPI, rather than 600 or higher. The dots are just to small at high resolutions for the plate material to pick up. If you want to try a quick test to see what I'm talking about, print a picture in greyscale on a laser at 600 DPI and then photocopy it. Now do the same only printing at 300. Which one comes out better? Check printers use this phenomena all the time. The background is printed at 300DPI with the exception of a pattern that spells out VOID printed at 600DPI. When photocopied, the word VOID can clearly be seen all over the copy, whereas with your eyes, it's hard to see the difference.