How to Fix White Boxes or Missing Characters in PDF Auto-Tagging
Question details
The user needs to resolve an issue where white boxes appear instead of text when running auto-tagging in Adobe Acrobat.
- Product
- Adobe Acrobat
- Device & OS
- not provided
- Scenario
- Running auto-tagging on a PDF document to improve accessibility and document structure.
- Observed behavior
- White square boxes (often called tofu characters) or missing characters appear instead of regular text, which usually indicates unembedded or missing fonts rather than a tagging defect.
Check if you have access to the original source file (e.g., Word, PowerPoint, or InDesign) used to create the PDF, as resolving missing font issues is most effectively done during the initial export process.
Embed Fonts and Export Directly from the Source Application
The most reliable way to resolve missing character issues is to re-export the PDF directly from the original authoring program with all fonts properly embedded.
White boxes (tofu characters) appear when the PDF viewer cannot find the fonts originally used in the document. This is not a bug with the auto-tagging feature itself, but rather a missing font issue.
Outdated PDF creation methods, such as using Acrobat Distiller, often strip out font data and structural tags. A modern PDF workflow involves exporting directly from the source application.
Open your original document in the program it was created in, such as a word processor or design software.
Navigate to the 'File' menu and select 'Export' or 'Save As', then choose PDF as your desired output format.
Before saving, check the PDF options or preferences in the save dialog. Look for a setting labeled 'Embed all fonts' or 'PDF/A compliance' and make sure it is checked.
Save the new PDF file. Open this newly generated PDF in Acrobat and run the auto-tagging process again to ensure the text renders correctly without white boxes.
Easily Create PDFs with Embedded Fonts Using WPS Office
Avoid missing fonts and tofu characters by using WPS Office's built-in PDF converter. It seamlessly embeds fonts from your documents to ensure perfect rendering and compatibility for auto-tagging.
- 1. Open Your Document in WPS Office: Launch WPS Office and open your original Word, Excel, or Presentation file.
- 2. Click Export to PDF: Go to the 'Tools' tab on the top ribbon and select the 'Export to PDF' button.
- 3. Configure Export Settings: In the dialog box, ensure the export options are set to generate a standard PDF, which automatically handles standard font embedding.
- 4. Export and Save: Click 'Export' to generate a clean, modern PDF ready for tagging or sharing without missing characters.
Frequently Asked Questions
What are tofu characters in a PDF document?
Tofu characters are the blank, white square boxes that appear when a PDF viewer or editor cannot render a specific font. It typically means the required font was not embedded in the file when the PDF was created.
Why shouldn't I use Acrobat Distiller to create PDFs?
Acrobat Distiller is an older technology designed for PostScript workflows. It often strips out modern document data, including essential font embeddings and structural tags needed for accessibility, which causes issues like missing characters during auto-tagging.
Can I fix missing fonts directly within the existing PDF?
While some advanced PDF editors offer preflight tools to embed missing fonts, you must have those exact fonts installed on your local system. It is generally much faster and more reliable to re-export the PDF from the original source file with font embedding enabled.
