Markdown files are being converted to PDFs with transparent background

[nbro10]

Explain the problem.

In most cases, when people want a PDF, they don't want it with a transparent background. By default, it seems that pandoc converts Markdown files to PDFs with a transparent background, which is very annoying because

1. this should definitely not be the default behaviour (i.e. white background should be the default behaviour, although it should support transparent background too)
2. there doesn't seem to be a flag to change this (but maybe I am wrong)

The workaround seems to be this ugly code

cat > /tmp/white-bg.tex <<'EOF'                               
\usepackage{xcolor}
\pagecolor{white}
EOF

pandoc x.md -o x.pdf -H /tmp/white-bg.tex 

Pandoc version?

pandoc 3.9.0.2
OS: Sequoia (Version 15.7.4)
pdfTeX 3.141592653-2.6-1.40.29 (TeX Live 2026) [kpathsea version 6.4.2]

pandoc and basictex were installed with brew

[bpj]

Routinely specifying \pagecolor{white} is a bad idea because that will induce printing devices to wastefully use white ink! Maybe not your cheap inkjet printer which probably doesn’t have white ink anyway, but fancier devices will. My grayscale laser printer once printed out a PDF with a light gray background making the text unreadable, and I didn’t understand why until I realized that the PDF specified an off-white background, which the printer driver interpreted as “not-quite-white”. I was able to make it use a somewhat higher white threshold and the thing printed out OK.

If your PDF viewer displays transparent-background PDF with a gray or checkerboard background the viewer is at fault because white should be the default for text documents. There probably is a setting for default background somewhere which you could and should set to white.

[nbro10]

@bpj I rarely encountered a case where I had to deal with a transparent-background PDF, and I work with PDFs every day. Yes, Acrobat shows the PDF with transparent background to have a transparent background by default (which is what you expect), although you can change it. The Preview app on mac actually shows it as white by default. To me it seems absurd that assuming that we want a white background is wrong. Paper is usually white. Online documents have white background. There's no reason to think that printing something on a white background is unexpected and should never lead to problems anyway.

[jgm]

These are LaTeX defaults (assuming you're using a LaTeX pdf-engine). Considering the huge number of PDF documents that have been produced this way, I don't see the default as problematic. Indeed, as @bpj points out, having an explicitly colored background can cause problems in some cases.

What is the problem, exactly, that the transparent background poses for you?
(Every PDF viewer I've tried displays it as white anyway.)