Changes corrupt font widths.
Corrupt font widths may occur in a PDF, when "artificial" bold or italic was used instead of the "bold" or "italic" version of the font concerned. For example, if "Futura" is used in your PDF, the "Futura-Bold" and "Futura-Oblique" fonts should be used instead of applying bold and italics on the regular Futura font. Artificial font may cause problems when printing the PDF.