If you're like me, you print out larger knitting patterns. Why? Cuz it is so danged difficult to not lose your place in a chart. On a read only PDF, unless the highlighting option has been enabled, you really have no other option than to print or to enlarge and keep the line you are working on at the bottom of your screen.
I have no idea why I never thought of this before. But I recently figured out how to create a sticky note in Windows 7 (I'm a little behind) and used that to place under the line in the chart I am working on (on top of the PDF). This way I don't have to print my pattern. It's more green. No wasting paper and ink. Not that I think others shouldn't print. But for me, I typically don't ever knit the pattern again. AND I am on my computer 24/7, so it just makes sense. (Plus I don't knit lace in knitting group, so I don't need to transport my pattern - it's too difficult for me to pay attention when I'm yapping!)
Here are the instructions for using Sticky Notes in Windows 7.
You can manipulate the size of the Sticky Note by dragging the borders. You can also make notations on the Sticky Note which is terrific for pattern notes you may need to make. You can make the Sticky Note any color you like as well. The Sticky Note will not disappear when you shut down your computer. It remains on the desktop or under Sticky Notes. You can delete at anytime and add as many as you like. JUST REMEMBER it will not stay attached to your PDF. You actually lay it over the PDF file. So, don't forget to notate on the Sticky Note what line you completed last (cuz when you close your pattern, your sticky will not stay with the pattern) so that when you open your Sticky Notes, you know where to start on your chart!
Instructions for using Sticky Notes In Vista -OR- XP via How To Geek.
Instructions for using Sticky Notes in Vista via Microsoft.