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Generating PDF files with shared fonts

Contents

Introduction

Specification of PDF 1.2 enables storing streams in external files. The streams, are used to embed Images, Page Descriptions, Fonts, etc. into PDF files. When creating document collection, storing an information shared by several PDF files into external files is reasonable approach. In practice, only fonts are a crutial material used by many PDF files in the same PDF collection.

BaKoMa TeX 2.21 supports generating PDF files with embeding fonts via external streams stored into common directory.

Efficiency of the method

This feature ables to create documents that share fonts. Such approach can drastically reduce size of document colections that include large number of PDF files. For example, typical conference procedengs (25 articles each is less then 10 pages in Computer Modern Fonts) processed with this approach requires 3 times less disk space then processed with partial font embedding into every article.

It is important that size of font-less PDF files are comparable with size of DVI files. This hint is useful to estimate size of a document collections.

Compatibility with another software

PDF files refered on external streams can be handled by following browsers:
  • Acrobat Reader 3.0 and later handle this feature.
  • GhostScript - beginning from version 5.25 it has code that must handle external streams. However, version 5.50 has some error in implementation of this feature. I hope, it will be fixed in version 6.0,
  • PDFtoPS (XPDF) don't understand this feature.
It is important, that this method is usefull for distribution of documents via CD-ROMs. However, this method is unusefull for uploading documents on WWW servers. The reason is that some PDF browsers can't handle font downloading via network.

Generating such PDF's by using BaKoMa TeX

Beginning from version 2.21 you can generate collection of PDF files that share fonts between each other. Sharing fonts is implemented by embedding fonts via external streams that are placed into separate directory.

To enable this feature choose `Embed to directory' option in PDF generation dialog. This option is available when PDFFonts subdirectory exists anywhere in: current directory, parent directory, grand parent directory, etc.

When font sharing is performed by BaKoMa TeX, fonts are placed into found PDFFonts directory, and relative references on the fonts are placed into PDF files. In this reason, PDF files can be freely moved together with PDFFonts directory and with preserving subdirectory structure.


Date: 3-Dec-1999.
Author: Basil K. Malyshev.