If the image is sharp but letters change shape, line breaks move or characters become empty boxes, inspect the typography rather than increasing image resolution. Check the actual font and its character coverage in the source document, then check font embedding in the exported PDF. Repair the source and re-export instead of repeatedly sharpening the page.
Sort the symptom before editing
A low-resolution photograph looks soft across the pictured detail. A substituted font changes the letterforms or spacing. A missing glyph can affect only one accented letter or one writing system while the rest of the page remains sharp. These problems can occur together, so compare a title, body line and image separately.
Open the PDF outside the layout application. Compare it with the source at similar zoom and read every line. If the source itself already contains a box, repair that text there first. PDF export cannot supply a character the chosen font does not contain.
Check font coverage and embedding
Confirm the exact typeface used, including its regular, bold and italic styles. Paste the real wording into the chosen font in the external layout application. Check accents, punctuation and all scripts; do not assume a font that displays English includes Chinese characters or every symbol.
Adobe’s font-embedding guidance explains full and subset embedding, as well as substitution when fonts are unavailable or restricted. Inspect the PDF’s font information using a capable PDF viewer. An embedded subset is not automatically a defect: it can intentionally include only used characters. The more useful question is whether the delivered wording renders as intended.
Adobe documents font settings within PDF conversion and their relationship to print standards. Use the printer’s required export preset and a legally usable font. A generic high-quality setting does not override a font’s embedding restriction or a missing character in the source.
A fictional bilingual invitation
Amira creates an invented invitation with “Café Evening” and a Chinese subtitle. The café artwork is sharp, but the accented é changes and two Chinese characters become boxes in the PDF. Amira compares the layout source with the export, then checks the text styles and selected fonts.
She replaces only the unsupported text style with an appropriate licensed font, checks the full subtitle and exports again. Her proof sheet records the exact wording, the intended line breaks and the final PDF filename. She prints the corrected title area at its intended size before approving the full invitation. No claim is made that this was a measured customer failure.
Keep the artwork and wording independent
Use Imagild Image Prompt for an appropriate visual treatment, then add final wording in an external layout application. If the lettering was generated as pixels inside the image, it is not a PDF font-substitution problem; rebuild that wording as verified text instead of adjusting embedding settings.
The final review should include names, numerals and punctuation, not just the headline. If the supplier requests outlined text, keep an editable master and inspect the outlined export carefully. Outlining changes the delivery structure and can reduce searchability or editing; it does not remove the need to proof the wording.
Will changing the PDF to 300 DPI fix missing letters?
No. Pixel density does not create missing glyphs or embed an unavailable font.
Can I fix the PDF without the original layout file?
Sometimes a PDF editor can make limited changes, but reconstructing the intended font and layout may be necessary. Obtain the source when accurate typography matters.