It's a little difficult to take an article on design too seriously when the font used is difficult to read (not stress, tall x-height) and when the PDF is not formatted for the media on which it is presented. Too often PDFs are simply thrown online, created from a "typical" 8.5x11 format, in portrait. At least turn it to landscape for onscreen reading so that a read if presented with a screenful of information at a time. Take a look at the Before & After newsletters for a good example of this in practice.
On the other hand if this PDF is intended to be printed before reading using a san-serif font is certainly a poor choice. Research seems to show that seriffed fonts are more readable in print.
Designing for specific devices
It's a little difficult to take an article on design too seriously when the font used is difficult to read (not stress, tall x-height) and when the PDF is not formatted for the media on which it is presented. Too often PDFs are simply thrown online, created from a "typical" 8.5x11 format, in portrait. At least turn it to landscape for onscreen reading so that a read if presented with a screenful of information at a time. Take a look at the Before & After newsletters for a good example of this in practice.
On the other hand if this PDF is intended to be printed before reading using a san-serif font is certainly a poor choice. Research seems to show that seriffed fonts are more readable in print.