Font Files
One of the great features in PDF is that font files can be embedded into PDF files, such that the PDF file can be rendered correctly even if that font is not available in the viewer's machine. On the other hand, font files can also be referred as names, and the PDF viewer will try to find that font, or a closest match if not found, in the viewer's machine.
In this article we discuss about pitfalls and considerations regarding font files in PDF, while optimizing output of pdf2htmlEX.
pdffonts is a handy tool supplied in the Poppler library. It shows the information of all the fonts used in a PDF file: name, type, encoding, embeded or not etc.
Here's a typical output of pdffonts.
name type encoding emb sub uni object ID
------------------------------------ ----------------- ---------------- --- --- --- ---------
Arial,Bold TrueType WinAnsi no no no 19 0
Arial TrueType WinAnsi no no no 20 0
NWBJZL+NimbusRomNo9L-MediItal Type 1 Custom yes yes no 30 0
FCXRUF+NimbusRomNo9L-ReguItal Type 1 Custom yes yes no 33 0
FQDHWA+NimbusRomNo9L-Regu-Slant_167 Type 1 Custom yes yes no 36 0
ZRUSRO+CMSY7 Type 1 Custom yes yes no 39 0
RBFYGC+Helvetica TrueType MacRoman yes yes no 48 0
TIVRUK+Helvetica-Bold TrueType MacRoman yes yes no 49 0
NVCFEO+Calibri-Bold TrueType WinAnsi yes yes yes 127 0
ZBVPYI+Calibri-Bold TrueType WinAnsi yes yes yes 142 0
In this case, all fonts are embedded in the PDF font except for the two Arial ones.
In the PDF specification, 14 standard fonts are supposed to be provided by any PDF viewer, so these fonts are often not embedded in order to save space. Some publishers/software choose not to embed some other font files assuming that all their viewers will have that font file installed.
Note that there are no such standard fonts defined in the Web standards, although some fonts are indeed available on almost all machines.
If a font file is not embedded in the PDF file, yet it cannot be found in the viewer's machine (not even a close one), usually a fallback font will be used, which is likely to cause rendering issues. Therefore pdf2htmlEX always embeds all matching fonts in the output, even if this might increase the output size a lot.
The reason it has been designed so is that, consider which one is more important for a newbie user who has no idea about all the details, rendering or size? This behavior can be changed via the --embed-external-font option.
Sometimes two or more font can be defined in PDF files, which are based on the same font file but with slight changes. pdf2htmlEX always see them as different fonts and generate separate files.
To fix this, you might want to optimize the PDF files before feeding them to pdf2htmlEX.