CAJ (.caj/.kdh/.nh) to Scanned PDF

Open CNKI CAJ, KDH and NH papers in your browser without installing CAJViewer. Preview every page, add paper tone, tilt and grain, then download a scanned PDF. Nothing is uploaded.

Processed locally, never uploadedSupports PDF, OFD, images, DOC/DOCX, ODT, PPT/PPTX, Excel, HWP, Markdown, HTML, RTF, EML, SVG, and TXT

Scan Settings

Choose color, grayscale or black & white output for the scanned document
Add a border around the scanned document
Adjust the rotation angle of the scanned document
Randomly vary the rotation angle of the scanned document
Adjust the brightness level of the scanned document
Adjust the contrast level of the scanned document
Adjust the blur level of the scanned document
Add noise effect to the scanned document
Add yellow effect to the scanned document
Set the scanning resolution in pixels per inch (PPI)

Paper Settings

Paper size of the output PDF and how pages are placed on the sheet
Paper size of the output PDF. A real scanner always outputs a fixed paper size; Auto keeps each page's original size.

Each page keeps its original size.

Signatures and Stamps Settings

A document stamp or signature is a light mark, text, or image added to the background of a document. It's often used to show ownership, protect the document, or add signatures.

Watermark Settings

A document watermark is a light mark, text, or image added to the background of a document. It's often used to show ownership, protect the document, or add a label like 'CONFIDENTIAL' or 'DRAFT'.
This feature is available only to Pro users
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The text that will be displayed as a watermark on your PDF
The image that will be displayed as a watermark on your PDF

PDF Metadata Settings

PDF metadata is information about a PDF document that describes its content, authorship, and other properties. It helps with organizing, searching, and categorizing the document without reading its actual content.
This feature is available only to Pro users
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The title represents the name of the document. It is typically intended to describe what the document is called and may be displayed in the title bar of PDF readers or in search results.
The author in a PDF's metadata represents the creator or originator of the document. It is intended to identify the person, organization, or entity responsible for the content of the document. This information is often displayed in PDF readers and can be used for attribution or search indexing.
The subject provides a short description or summary of the document's content. It serves as a brief explanation of what the document is about.
Keywords help describe and categorize the document content. They can be used for searching and organizing PDFs in document management systems.
The producer indicates which software or system generated the PDF file. It helps identify the tool used to create or modify the document.
The creator indicates which software or system created the PDF file. It helps identify the application used to generate the document.
The creation date indicates when the document was originally created. This metadata helps track the document's origin and timeline.
The modification date indicates when the document was last changed. This metadata helps track the document's revision history.
PDF/A is an ISO standard for long-term PDF archiving. Many scanners and “Scan to PDF” apps save files as PDF/A, so enabling it makes the output resemble a genuine scan more closely. PDF/A-1b offers the broadest compatibility, while PDF/A-2b produces smaller files.

Output Settings

Choose the format and filename of the scanned result
Save the scan as one PDF, or as one image per page inside a ZIP archive.
Upload a PDF, DOCX, PPTX, Typst or CAJ file to use this option. Only existing text is kept; text in images is not recognized.
Upload a PDF, DOCX, PPTX, Typst or CAJ file to use this option. Only existing text is kept; text in images is not recognized.
Added to the end of the original filename. Leave it empty to keep the original filename.

Files will be saved as “example-scan.pdf”

Image preview

How to turn a CAJ file into a scanned PDF

  1. Select the .caj, .kdh or .nh file you downloaded from CNKI. It is converted in your browser and its pages appear in the original preview.
  2. Check that body text, equations and figures are clear, then adjust paper tone, tilt and grain so small print stays readable.
  3. Select “Generate Scanned PDF”, then “Download Scanned PDF” to save the paper’s pages with the scan effect.

Supported formats

Frequently asked questions

What is a CAJ file, and can I open it without CAJViewer?

CAJ is the proprietary format of CNKI (China National Knowledge Infrastructure); .kdh and .nh belong to the same family, and theses often download as .nh or .caj. They usually need CNKI’s CAJViewer. Here nothing needs installing: the file is converted to PDF in your browser and then shown, on Windows, Mac, Linux or a phone.

Does every CAJ file convert?

Most .caj and .kdh files convert directly. Pages stored in HN or C8 encoding, common in .nh theses, are supported experimentally and some files may not open; the TEB format is not supported. The table of contents (bookmarks) is not kept. If a file fails you see an error message, and the PDF edition from CNKI, where offered, is the alternative.

Can I search or copy the text in the PDF afterwards?

Not by default: as with a real scan, every page is saved as an image. When saving a PDF, turn on “Preserve original text (OCR-like)” in Output Settings and the text already in the CAJ file stays searchable and copyable. Pages stored as images have no text to keep, and no OCR is performed.

Are my files uploaded to a server?

Standard and bulk scanning process source documents in your browser without sending those files to a processing server. HTML files may load linked online resources such as images or fonts while they are rendered. Word, PowerPoint and Excel may download missing fonts; source documents stay on your device.

Is it free, and is there a limit?

Standard scanning is free and needs no signup. Free scans have a fixed daily limit; Pro lifts it and also unlocks bulk scanning, an ad-free workspace and API access.