You hit print on a PDF that looks perfect on your screen. The printer whirs to life, pages slide out, and the result is wrong. Letters are missing from words. Where there should be readable text, there are empty rectangular boxes, sometimes called tofu by typographers. Or the text is there but portions of it appear as blank white gaps between fragments of letters. The document looked fine a moment ago. What happened between the screen and the paper?
This problem is familiar to anyone who regularly prints PDFs from different sources. The Allyant PDF Accessibility Index for 2025-2026, which examined over 644,000 public-facing PDFs, found that structural issues including missing font data affected a significant portion of documents, with 94.75% failing basic usability standards (Allyant, "PDF Accessibility Index", 2026). While not every failure manifested as a printing problem, the underlying cause is often the same: incomplete or mismatched font information embedded in the file.
Missing Fonts Are the Most Common Reason for Printing Gaps
When a PDF is created, the software that generates it decides whether to embed the PDF Fonts data inside the file or to simply reference the font by name and assume the viewer or printer will have it available. If the font is embedded, the PDF carries everything needed to render the text correctly on any device, including a printer that has no fonts installed at all. If the font is not embedded, the PDF depends on the printer or operating system to supply a matching font. When the printer does not have the font, the text cannot be rendered, and you get blank spaces, tofu boxes, or entirely missing characters.
This problem is especially common with PDFs created by applications that use non-standard or licensed fonts. A marketing brochure designed in Adobe InDesign using a premium typeface, a financial report exported from a specialized accounting application, or a PDF generated by a web browser from a page that loads fonts from a CDN all carry the risk of font substitution at print time. The screen display works because modern PDF viewers have sophisticated font fallback mechanisms. The printer, which processes the file through a different rendering pipeline, may not have access to the same fallback logic.
How Font Substitution Produces Square Boxes and Blank Spaces
When a printer encounters a font it does not recognize, it has limited options. Some printers substitute a generic built-in font, such as Courier or Helvetica, in place of the missing font. The text prints, but it looks wrong. The spacing is off, the letter shapes do not match, and the overall appearance of the document is compromised. This is the best-case scenario among font-related failures because at least the content is legible.
Other printers, particularly older models and some network printers, do not perform font substitution at all. When they encounter a missing font, they print blank spaces where the text should be. The document emerges from the printer with gaps in sentences, words cut in half, or whole paragraphs reduced to ghostly white rectangles. The printer is not malfunctioning. It is faithfully reporting that it does not have the data it needs to do its job.
The square box or tofu problem occurs when a printer partially recognizes a font. It has enough font data to know that characters exist at certain positions, but the specific glyphs, the actual shapes of the letters, are missing from its font tables. The printer outputs a rectangle as a placeholder for each missing glyph. This is most common with PDFs containing special characters, symbols, mathematical notation, or non-Latin scripts like Chinese, Japanese, Arabic, or Cyrillic, where the printer's built-in font set is unlikely to include the needed character shapes.
Corrupted or Incompletely Downloaded PDFs Can Cause Similar Symptoms
Font problems are the most frequent cause of printed text gaps, but they are not the only one. A partially downloaded or corrupted PDF file can produce nearly identical symptoms. If a PDF is interrupted during download, such as when a web browser times out or a network connection drops, the file may appear to open correctly on screen while containing damaged internal structures that only become apparent when the printer processes the file more strictly than the screen viewer did.
PDF files have an internal cross-reference table that maps every object in the file, fonts, images, text streams, metadata, to its byte position. If this table is incomplete or corrupted, objects near the end of the file may be unreachable by the rendering engine. A screen viewer might silently skip these unreachable objects and display what it can. A printer's RIP (Raster Image Processor) may be less forgiving and produce missing elements, blank pages, or an outright failure to print.
The simplest way to test whether corruption is involved is to download the file again and try printing the fresh copy. If the problem disappears, the original download was the culprit. If the problem persists across multiple downloads, the issue is likely in the PDF itself, most commonly a font embedding problem.
How to Fix the Problem Before Sending the PDF to Someone Else
If you control the creation of the PDF, the fix is straightforward. Always select the option to embed fonts when exporting or saving as PDF. In Microsoft Word, this setting lives under Options in the Save As PDF dialog. In Adobe InDesign and Illustrator, font embedding is controlled in the Export settings under the Advanced panel. In Google Docs, fonts are automatically embedded when you download as PDF. In most web browsers, the Print to PDF function embeds the fonts used by the page at the time of printing, though web fonts loaded dynamically via JavaScript may be missed.
If you received the PDF from someone else and it prints with missing text, the most reliable fix is to use PDF Editor software to re-export or flatten the document. Opening the file in a PDF editor and printing it to a new PDF, sometimes called "refrying" the PDF, forces the rendering engine to resolve all font references and embed the actual glyph shapes into the output. The resulting file will be larger because it now contains all the font data, but it will print correctly on any printer. WukongPDF handles this process automatically when you use its editing tools on a file, embedding the necessary font data in the output so the recipient does not encounter font-related printing problems.
A Second Diagnostic Tool: The Print as Image Workaround
Nearly every PDF viewer includes an option to "Print as Image" in its advanced print settings. When this option is enabled, the viewer renders each page to a bitmap image and sends that image to the printer instead of sending the structured PDF data. The printer receives a photograph of the page rather than instructions to draw text using specific fonts.
Print as Image bypasses font embedding issues entirely because no font data needs to be transmitted to the printer. Every character, every symbol, and every line is pre-rendered into pixels. The trade-off is that the printed output may not be as sharp as a properly font-rendered print, and the print job will take longer to spool because the data volume is much larger. But when you need a document to print correctly right now, this workaround almost always works.
If Print as Image also produces blank spaces or missing text, the problem is not font-related. It may be a printer driver issue, a corrupted PDF, or a hardware problem with the printer itself. In that case, updating the printer driver, trying a different printer, or re-downloading the file are the most productive next steps.