How a font-free Alpine container silently rendered blank legal document pages

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A developer building e-signature platform Putmysign discovered that certificate pages were rendering completely blank in production despite no errors or failed exit codes. The root cause was that the Node 24 Alpine Docker container shipped with no system fonts, so when pdftoppm tried to render PDFs using standard base-14 fonts like Helvetica, it found no substitutes and drew nothing. Installing Liberation fonts — metric-compatible replacements for the base-14 families — resolved the blank-page issue with a single Dockerfile line. A second bug was also uncovered: typed signatures displayed in Dancing Script font were being saved in PDFs as Helvetica Oblique, because the font file was unavailable at runtime in the production image. The incidents highlighted that fonts are a deployment concern, and that a renderer returning exit code 0 is no guarantee the output is correct.

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