I created a brochure out of Illustrator CS4 on a Mac. It printed clearly, without a glitch, at the press shop.
However, when I tried to produce a web-version PDF for download, it caused a very strange problem where the letters "L", and the uppercase "i" showed up extra thick and extra tall, ONLY on acrobat readers. This was observed on my Acrobat Pro on my Macbook Pro, as well as on my client's Adobe Acrobat Reader on a Windows PC. However when I open this file on my computer using Preview, or even using Gmail's PDF preview, the letters show up fine.
The steps taken:
1. The text in question was, of course, initially text layers. However this was converted to outlines of text when it was moved to the PDF, to avoid issues where a user without the Century Gothic font could still view the brochure as it was intended to.
2. While saving to PDF, raster graphics were reduced to 300ppi, and illustrator editability was taken away.
The produced PDF was this mess. Here are screenshots - one screenshot of reading it in Preview, the other in Acrobat. Files were also attached to this question for your convenience.