The fontconfig package, installed on the GNU/Linux host, is used by the PDF printing renderer to get the best matching installed font as substitute for non-embedded fonts in the PDF document.

The PDF "Standard 14 fonts"^[51] aka "Base 14 Fonts" are never embedded. Every PDF renderer is required to provide these fonts, either directly or via appropriate substitutes. Current substitutes are shown in the Admin Web App, About Host Packages section.

When a PDF document contains non-embedded fonts that are not from the Standard 14 fonts, the substitute fonts selected by fontconfig may not be the same as the fonts used to create the PDF, and so rendering may not be correct. Therefore, it is wise to install additional fonts, especially the much used Microsoft True Type Core Fonts with Andale Mono, Arial, Comic Sans MS, Courier New, Georgia, Impact, Times New Roman, Verdana, etc.

# DejaVu provides an expanded version of the Vera font family aiming for
# quality and broader Unicode coverage while retaining the original Vera style.
sudo apt install fonts-dejavu

# Other fonts for more accurate matching, so non-embedded fonts
# don't fallback to DejaVu font.

# Microsoft True Type Core Fonts
sudo apt install ttf-mscorefonts-installer

# Free look-alike fonts of the Adobe PostScript fonts:
# Nimbus Roman, Nimbus Mono, Nimbus Sans, Century Schoolbook, Dingbats, 
# Standard Symbols, URW Chancery, URW Palladio, URW Gothic, URW Bookman
sudo apt install gsfonts

# Cantarell sans serif font family designed for on-screen readability.
sudo apt install fonts-cantarell

# Width-compatible fonts for improved on-screen readability
# Arimo, Cousine and Tinos are metrically compatible with Arial,
# Courier New and Times New Roman, respectively.
sudo apt install fonts-croscore

# Caladea is metric-compatible with Cambria font.
sudo apt install fonts-crosextra-caladea

# Carlito is metric-compatible with Calibri font. 
sudo apt install fonts-crosextra-carlito

# Extensive character set coverage including Western Europe, Eastern/Central Europe, 
# Baltic, Cyrillic, Greek and Turkish support. The Droid Sans regular font also
# includes support for Arabic, Simplified and Traditional Chinese, Hebrew, Japanese, 
# Korean and Thai.
sudo apt install fonts-droid-fallback 

# Fonts with the same metrics as Times, Arial and Courier
sudo apt install fonts-liberation

# "Noto" is short for "No Tofu", describing the aim of covering
# all living Unicode scripts.
sudo apt install fonts-noto

# OpenSymbol TrueType font included in LibreOffice.
sudo apt install fonts-opensymbol