Merge pull request #578 from telerik/new-kb-validating-fonts-document-processing-9ec1f0c564dd4019abd164280fc1feea

Added new kb article validating-fonts-document-processing

Author: dessyordanova

knowledge-base/validating-fonts-document-processing.md

@@ -0,0 +1,63 @@
+---
+title: Validating Fonts when Using Telerik Document Processing
+description: Learn how to identify incomplete or corrupt TTF font files that cause content issues while exporting PDF files using Telerik Document Processing.
+type: how-to
+page_title: Identifying incomplete or corrupted font files causing content issues in exported PDF dcouments
+meta_title: Identifying incomplete or corrupted font files causing content issues in exported PDF documents
+slug: validating-fonts-pdf-document-processing
+tags: word, document, processing, ttf, font, validation, pdf, export, spread, fixed, flow, excel
+res_type: kb
+ticketid: 1690314
+---
+
+## Environment
+
+| Version | Product | Author | 
+| ---- | ---- | ---- | 
+| 2025.2.520| Telerik Document Processing |[Desislava Yordanova](https://www.telerik.com/blogs/author/desislava-yordanova)| 
+
+## Description
+
+When exporting a document to PDF format using the Telerik [Document Processing Librararies]({%slug introduction%}), content issues may occur due to incomplete or corrupted font files. These issues can arise if the font file is incomplete, corrupted, or missing required font tables. This results in missing or improperly rendered text in the exported PDF.
+
+This knowledge base article gives some tips and tricks how to validate fonts used in Telerik Document Processing and what tools can check for font file's integrity.
+
+## Solution
+
+To ensure a font file is complete and compatible with Telerik Document Processing, follow these steps:
+
+* **Open the Font in a Font Viewer**  
+
+   Double-click the TTF file to open it in the system font viewer. Inspect whether all expected characters display correctly and ensure no error messages appear.
+
+* **Test the Font in Other Applications**  
+
+   Install the font on your system and use it in applications like Word or Notepad. Verify that all characters render correctly.
+
+* **Compare File Size and Metadata**  
+
+   Compare the file size and properties of the font with an official or known-good version. Noticeable differences can indicate corruption or missing data.
+
+* **Use Font Validation Tools**  
+   Validate the font file with tools like:
+   - [FontForge](https://fontforge.org/)  
+   - [Microsoft Font Validator](https://github.com/Microsoft/Font-Validator)  
+   These tools check for missing tables, corrupt glyphs, and other font-related issues.
+
+* **Check Required Styles**  
+
+   Verify that all required styles (Regular, Bold, Italic, etc.) are available if your document uses them. Missing styles can cause fallback or rendering issues.
+
+### Recommendations
+
+- Validate fonts from third-party sources before integrating them.
+- Request official font packages or sources for reliable compatibility.
+- Replace problematic font files with known-good versions to resolve rendering issues.
+- You can utilize a [FontsProvider]({%slug pdfprocessing-implement-fontsprovider%}) implementation to identify all fonts and styles used in the document. Thus, you can log missing or problematic fonts during testing for early detection.
+
+## See Also
+
+- [FontForge](https://fontforge.org/)  
+- [Microsoft Font Validator](https://github.com/Microsoft/Font-Validator)  
+- [Fonts - Cross-Platform support]({%slug radpdfprocessing-cross-platform-fonts%})  
+- [Standard Fonts in PdfProcessing]({%slug radpdfprocessing-concepts-fonts%})

libraries/radpdfprocessing/concepts/fonts.md

@@ -164,6 +164,6 @@ You can create fonts that are not explicitly registered. Creating a font that is
  * [FontsRepository](https://docs.telerik.com/devtools/document-processing/api/Telerik.Windows.Documents.Fixed.Model.Fonts.FontsRepository.html)
  * [TextFragment]({%slug radpdfprocessing-model-textfragment%})
  * [Preserving the Font in PDF Export from Excel]({%slug preserve-font-boldness-pdf-export-radspreadprocessing%})
- * [How to Prevent Text with Special Characters from Being Cut Off when converting HTML to PDF using RadWordsProcessing]({%slug prevent-text-cut-off-pdf-conversion-radwordsprocessing%})
+ * [How to Prevent Text with Special Characters from Being Cut Off when converting HTML to PDF using RadWordsProcessing]({%slug prevent-text-cut-off-pdf-conversion-radwordsprocessing%}) 
+ * [Validating Fonts when Using Telerik Document Processing]({%slug validating-fonts-pdf-document-processing%})
  * [Resolving Apostrophe Character Being Replaced with Copyright Symbol in Filled PDF AcroForm]({%slug apostrophe-character-replaced-copyright-symbol-acroform%})
-

libraries/radpdfprocessing/cross-platform/fonts.md

@@ -27,4 +27,5 @@ You can find a detailed **FixedExtensibilityManager** and **FontsProvider** desc
  * [Inserting Special Symbols in PDF using RadPdfProcessing]({%slug inserting-special-symbols-pdf-radpdfprocessing%})
  * [How to Eliminate Formatting Issues when Exporting XLSX to PDF Format]({%slug exporting-xlsx-to-pdf-formatting-issues%})
  * [Resolving Missing Content in Exported PDF Files]({%slug missing-content-word-to-pdf-radwordsprocessing%})
+ * [Validating Fonts when Using Telerik Document Processing]({%slug validating-fonts-pdf-document-processing%})