CAJ to PDF: Complete Guide to Converting CNKI Academic Papers

Got a .caj file that won't open, can't be annotated, or isn't recognized by your reference manager? Upload it to CAJ to PDF for instant online conversion — no need to install CAJViewer, works on Mac / Linux / mobile.

What Is CAJ? Why Convert It?

CAJ (China Academic Journal) is a proprietary academic document format developed by CNKI (China National Knowledge Infrastructure). Born in the late 1990s when internet bandwidth was scarce, it achieved high compression ratios and copyright control through layered compression and built-in DRM — genuinely useful in the dial-up era.

Today, however, the inconveniences are hard to ignore:

Converting CAJ to the universal PDF format is the most straightforward solution — as an ISO international standard, PDF can be opened on virtually any device and integrates seamlessly with reference management and annotation tools.

Online Conversion: 3 Steps

CAJ to PDF lets you upload .caj files and convert them to standard PDF directly.

Step 1: Upload Your CAJ File

Open CAJ to PDF and drag your file into the upload area.

Step 2: Wait for Automatic Conversion

The tool parses the CAJ file and repackages it as PDF in the background — no manual intervention needed.

Step 3: Download and Verify

After conversion, download the PDF and check:

• Flip through each page to confirm content is complete
• Use Ctrl+F to test whether text is searchable
• Check that charts and formulas display correctly

Advanced Tip: Get PDF Directly from CNKI

If your paper hasn't been downloaded yet, there's a way to skip CAJ entirely and get native PDF.

Install the Tampermonkey browser extension and search for a CNKI PDF download script. The script modifies the download page logic to redirect to an interface that provides PDF downloads. The resulting PDF is officially packaged by CNKI, with high text layer accuracy and complete hyperlinks.

Virtual Printing: Fallback When Conversion Fails

In rare cases, CAJ files with extreme encryption or unusual formatting may resist all conversion tools. Virtual printing serves as a last resort:

1. Open the file in CAJViewer (version 7.2 recommended for better print compatibility)
2. Select Microsoft Print to PDF as the virtual printer
3. Set high-quality DPI output and save

This method renders pages through the operating system's print engine, bypassing most format compatibility issues with precise layout. However, it will lose the original table of contents bookmarks, which need to be rebuilt manually (see below).

Post-Conversion Fixes

Most CAJ files convert smoothly, but due to CAJ's non-standard encoding and proprietary data structures, some files may need post-conversion fixes.

Garbled Text: Character Encoding Issues

CAJ stores characters using non-standard encoding tables. When the converted PDF renders with system fonts, character mapping offsets can cause square boxes or garbled text.

Possible fixes:

• For scanned CAJ documents, use OCR to re-recognize the text layer after conversion — this usually resolves most garbled text
• In a PDF editor, select "Embed All Fonts" and re-save
• For English font anomalies, try forcing CID (Character Identifier) font mapping

Missing Table of Contents

Some conversion methods (especially virtual printing) lose the original sidebar bookmarks, which is inconvenient for dissertations spanning hundreds of pages.

Rebuilding options:

1. Via Word: Use PDF to Word to export → generate table of contents automatically in Word using heading styles → export back to PDF
2. Manual: Use a PDF editor to manually add bookmark jumps for each chapter

Scanned Text Not Searchable

If the original CAJ consists of scanned page images, the converted PDF still won't have searchable text. Use OCR for full-text recognition to generate a searchable transparent text layer.

Scenario Quick Reference

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