I did some experimentation. I'm still using IE8 because IE9+ text issues but may have found a solution.
By using a good quality CRT (reads fine->) in 1600x1200, and then in windows 7 setting "make text and other items smaller/larges" control panels "Set custom size (DPI)" to 130% and selecting "Use Windows XP style DPI scaling", in the IE10 preview that I have installed text actually becomes much like GDI text. (Zoomed in 300% to look at the pixels for a font known to be unreadable in IE9/10 normally).
Of course this means I don't quite get the full use of 1600x1200 and it looks more like something near 1280x1024 desktop, but atleast the text is quite readable and the only thing I'd like is a CRT with 3200x2400 resolution or more at maybe 25" size.
The key here is that the DPI zoom % should be set so that the most commonly seen worst scenarios with IE9/10 font rendering actually become non-issue. Where normally at the default setting the "i" "l" "m" "h" etc have the vertical likes rendered with only blue and red color (seen easily zoomed in mspaint and just look fuzzy when not zoomed in), at around 130% zoom they start to be rendered mostly normally. I didn't test many cases though yet , just the couple worst cases I've seen.
what does this have to do with *FIREFOX* ?? the OP was talking about how FIREFOX does PDF files ? are you lost or what am I missing in this reply ?