Start > Optimization > Overview > "Text/Graphic" Tab
In this tab, you can convert text to graphics, choke graphics (term from trapping for "make smaller" in contrast to "overlap") and convert small graphics to bitmaps.
Text
Convert Text to Graphics
All text elements in a PDF document of the font type selected ("Type1 (PostScript)", "TrueType" or "OpenType") are converted to vector graphic elements if you enable one of these options in this group. This requires that the fonts are embedded either in the PDF document or can be found in the font search folders. Other font types are not converted.
You cannot edit converted text elements. During proofing, the font appears bolder than in the original format.
Graphics
Choke Graphics
This option is designed for cases where you want to print fonts converted to graphics on low-resolution printers. Because graphics are screened differently to fonts, these fonts are too "bold" when output. The PDF originals come with converted fonts that in most cases cannot be mapped to variants with embedded fonts.
In such cases, enabling the "Choke Graphics by..." option lets you print the fonts less bold. The rate can be set in the input box.
In the box "if neutral density is above", you can specify a threshold starting from which the line weight of the outline fonts will be reduced. For details, see: What is neutral density?.
Turn Small Graphics into Bitmaps
This option is designed for cases where, for example, fonts converted to paths, like those created by ArtPro, are to be printed using inkjets. Such (vector) graphics, especially low-resolution ones, are often too bold when printed. When this option is enabled, these graphics are converted to bitmaps, preferably in the print resolution (e.g. 1200 dpi). This works around the effect of printing being too bold.
In the "Size Limit" box you can set the maximum size the graphics may have to be converted into bitmaps.
Conversion to bitmaps is advisable only for dark fonts on a light background. In the "if neutral density is above" box, you can specify a threshold for neutral density above which small graphics will be converted to bitmaps.
You should enter the resolution used in printing in the "Resolution" box.