Working with Vector Graphics
One of the biggest, usually undiscovered, strengths of the PDF file format is that it can contain and maintain (not change in any way) vector graphics, such as those created with Adobe Illustrator. Vector object information is saved entirely within a PDF document; this allows the vector graphics to be displayed at any zoom level, and still maintain "perfect" quality. Another advantage of vector graphics is that using them can take up less space than an equivalent bitmap image.
Unfortunately, the opposite is also true of detailed vector graphics, especially those with large amounts of type that have been converted into outlines. In fact, when creating vector graphics for placement in PDF files, it's almost never a good idea to change type to outlines (unless some special effect needs to be applied to the text which can only be done to outlined paths). The more detail in a vector graphic, the more space it will consume (on a disk).
However, this detail can be useful if the physical size of the graphic is limited to a small amount of square inches, because Acrobat Reader can zoom in to the artwork dramatically, increasing detail.
You can keep file size to a minimum by creating PDF files from software that doesn't require you to save Illustrator documents as EPS before placing them into page layout programs. Adobe Illustrator, InDesign, and PageMaker allow you to do this.