Well, first off, check you options for the TEXT sheet Effects. Looks like it has a slight blur, which could be causing your issues.

Having never used PDF Creator, it could be a limitation of that software. Try Cute PDF and when printing choose tile printing to print it to multiple sheets maybe that might help your resolution.

Also, check under:

TOOLS -> OPTIONS

Then select BMP,JPEG, PNG button.

Even though the field in the upper left says BITMAP SIZE it affects Bitmaps, Jpegs and PNGS.

Good Luck