--- title: "CAJ to PDF: open CNKI papers without CAJViewer and turn them into scanned PDFs" description: "Look Scanned now opens CNKI's CAJ, KDH and NH files. Check every page of a paper in your browser, add a scan effect and download a PDF that opens on any device." date: 2026-10-08T08:00:00.000Z lang: en source: https://lookscanned.io/en/blog/caj-to-scanned-pdf tags: ["CAJ", "CNKI", "PDF", "product updates"] --- # CAJ to PDF: open CNKI papers without CAJViewer and turn them into scanned PDFs Download a paper from CNKI, the Chinese academic database, and there's a good chance you get a `.caj` or `.nh` file instead of a PDF, especially for master's and doctoral theses. On Windows you first have to install CAJViewer; on a Mac, on Linux, on a tablet or a phone, it's often unclear what can open it at all. Look Scanned can now open these files. Go to [CAJ to Scanned PDF](https://lookscanned.io/en/scan/caj), select the file, and the paper is converted in your browser and shown page by page. Check it, add a scan effect and download a PDF that opens on any device. No CAJViewer to install and no account to sign in to. ## What are CAJ, KDH and NH files? CAJ is the proprietary document format of CNKI (China National Knowledge Infrastructure), and CAJViewer is the reader CNKI built for it. Two more extensions belong to the same family, `.kdh` and `.nh`; `.nh` is common for master's and doctoral theses. Ordinary PDF readers and browsers can't open any of them. Look Scanned converts the file to PDF in your browser with the open-source caj2pdf-rust converter, then shows and scans it like any other PDF. ## Which files convert? - **`.caj` and `.kdh`**: most files convert directly. Text, equations and figures appear as they are on the page. - **`.nh` theses**: pages stored in HN or C8 encoding are supported experimentally, and some files may not convert. When one fails you see an error message rather than a broken PDF. The converter detects the encoding from the file's contents, so a `.caj` file holding these pages is handled the same way. - **TEB format**: not supported yet. - **Table of contents (bookmarks)**: not kept. The scanned PDF is a series of page images, so the original outline doesn't carry over. If a file won't open, check whether CNKI offers a PDF edition of the same paper, then drop that PDF into Look Scanned instead. ## How do I turn a CAJ file into a scanned PDF? 1. Open [CAJ to Scanned PDF](https://lookscanned.io/en/scan/caj) and select your `.caj`, `.kdh` or `.nh` file. 2. Wait for the conversion to finish, then go through the preview and check body text, equations, tables and images. 3. Adjust the scan effect, such as paper tone, tilt and grain. Papers are full of small print and formulas, so keep blur and noise low to keep them readable. 4. Select "Generate Scanned PDF", then "Download Scanned PDF". Long papers take a little while to convert and generate; the more pages, the longer it takes. If you have several papers, Pro's [Bulk Scan](https://lookscanned.io/en/scan/bulk) handles them in one go, with CAJ and PDF files mixed together. For one image per page, switch the output format to PNG or JPEG; [scanned PDF vs JPG vs PNG](https://lookscanned.io/en/blog/scanned-document-pdf-jpg-png) explains the difference. ## Can I still search and copy the text? Like a real scan, the PDF stores every page as an image by default, so the text can't be selected. If you still need to search and copy, turn on "Preserve original text (OCR-like)" in Output Settings when saving a PDF. `.caj` pages usually carry a text layer, and that text is written into the scanned PDF as it is: the pages look scanned, yet the text stays searchable and copyable. This isn't OCR. Pages stored as images, as in most `.nh` theses, have no text to begin with, so there's nothing to keep. ## Your file stays on your device Conversion and scanning both happen in your browser, and the paper is never uploaded to a server. The converter is a WebAssembly module loaded from Look Scanned's own site, and it sends no requests anywhere else. Once loaded, your browser caches it, so CAJ files open offline too. ## Good to know - **Respect copyright and licence terms.** CNKI papers are protected by copyright, and downloading and using them is governed by CNKI's terms and your university's or institution's licence. Only process files you're allowed to use; converting to PDF doesn't change those limits. - **A scan effect is always added.** Making documents look scanned is what Look Scanned is for. If all you need is a clean PDF, use CNKI's PDF edition where one is offered. - **Compare the preview before sending.** HN/C8 support is still maturing, and an occasional page may differ slightly from what CAJViewer shows. For important files, check every page before you generate. OFD, another fixed-layout format from China, works [the same way](https://lookscanned.io/en/blog/ofd-to-scanned-pdf). Got a CAJ file you couldn't open? [Try it now](https://lookscanned.io/en/scan/caj).