Convert CHM to PDF — Free Online Converter
Convert Compiled HTML Help (.chm) to Portable Document Format (.pdf) online for free. Fast, secure document conversion with no watermarks or registrat...
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How to Convert
Upload your .chm file by dragging it into the upload area or clicking to browse.
Choose your output settings. The default settings work great for most files.
Click Convert and download your .pdf file when it's ready.
About CHM to PDF Conversion
CHM (Compiled HTML Help) is Microsoft's legacy help documentation format — a compressed archive of HTML pages, images, and navigation files used as software manuals and technical references since Windows 98. PDF (Portable Document Format) is the universal document standard for sharing, printing, and archiving. Converting CHM to PDF transforms proprietary Windows help files into universally accessible documents that can be viewed, printed, and annotated on every device and platform.
This conversion is the standard approach for making legacy software documentation available outside the Windows Help ecosystem. PDF preserves the visual formatting of the CHM content while adding document features like bookmarks, page numbers, searchable text, and print-ready layout that CHM's browser-like rendering cannot provide.
Why Convert CHM to PDF?
CHM files are increasingly inaccessible. macOS treats CHM as a potential security risk (quarantine attribute blocks opening), Linux requires third-party viewers, and no mobile platform supports CHM natively. PDF eliminates all platform compatibility issues — every computer, tablet, and phone can display PDF documents without specialized software. For organizations with legacy CHM documentation, PDF conversion is the simplest path to universal access.
PDF also serves documentation workflows that CHM cannot. Printed reference manuals, annotated review copies, formal submissions to regulatory bodies, and archival in document management systems all require PDF. CHM was designed for on-screen help within Windows applications — it was never intended for printing, distribution, or long-term preservation. PDF addresses all of these use cases while maintaining the formatted content of the original help file.
Common Use Cases
- Print legacy software documentation from CHM format as paginated PDF reference manuals
- Share CHM technical guides with macOS and Linux users who cannot open CHM files natively
- Archive CHM help file collections as PDF in institutional document management systems
- Convert CHM API documentation to PDF for offline reference by development teams
- Submit CHM-based compliance or regulatory documentation as PDF to authorities that require it
How It Works
Calibre extracts the CHM archive, parsing HTML content pages, the HHC navigation file, and embedded resources (images, CSS). The HTML content is rendered with CSS styling into paginated PDF output using Calibre's PDF engine. Page size, margins, font, and spacing are configurable. The CHM's table of contents (HHC file) generates PDF bookmarks for sidebar navigation. Images are embedded at their original resolution. The output includes embedded fonts, vector text for searchability, and proper page numbering. The PDF conforms to standard specifications and is compatible with all PDF viewers.
Quality & Performance
Text content, headings, lists, tables, and code blocks from the CHM transfer with high fidelity to the PDF. Images are embedded at their original resolution. The PDF bookmarks generated from the CHM table of contents provide easy navigation. The main quality considerations involve the CHM-to-print transition: CHM pages designed for variable-width browser rendering must be repaginated for fixed-size PDF pages. Long code blocks may wrap differently, wide tables may need scaling, and some CSS layouts may reflow. For standard technical documentation, the output is clean and professional.
Device Compatibility
| Device | CHM | |
|---|---|---|
| Windows PC | Partial | Partial |
| macOS | Partial | Partial |
| iPhone/iPad | Partial | Partial |
| Android | Partial | Partial |
| Linux | Partial | Native |
| Web Browser | No | Native |
Tips for Best Results
- 1Use PDF bookmarks (generated from CHM table of contents) to navigate the converted document efficiently
- 2Choose a page size appropriate for your use — A4 for standard documents, Letter for US printing
- 3For programming references, verify that code examples render correctly with the selected font and page width
- 4Unblock downloaded CHM files in Windows (right-click, Properties, Unblock) before converting to avoid extraction errors
- 5Consider converting to EPUB instead if you plan to read the content on e-readers or mobile devices
CHM-to-PDF conversion produces universally accessible, printable, and archivable documents from legacy Windows help files, preserving content and navigation while eliminating platform dependency.