1. Download and configure GroupDocs Viewer for Java v1.4 from this page https://groupdocs.com/Community/files/9/java-libraries/groupdocs_viewer_for_java/default.aspx
2. Start Viewer (read documentation for see how to do it).
3. Configure DNN plugin to use started service.

1. Download installation package (for example dnn_groupdocs_viewer_java_01.00.00_Install.zip, you can download it via RAW option of the github).
2. Install the module with DNN Platform v7
3. Add the installed module to any page, via Edit Page, Modules->Add new module
4. Press configuration button for the added GroupDocs Viewer for Java block
5. Provide required configuration options on "GroupDocs Viewer for Java Settings" tab.
6. Press update and GroupDocs Viewer for Java v1.4 will be integrated into the page as a jQuery plugin.

Also you can look screencast about installation process

Server URL - Example: https://localhost:2222

Default file name - Example: candy.pdf

###Sign, Manage, Annotate, Assemble, Compare and Convert Documents with GroupDocs

1. Sign documents online with GroupDocs Signature
2. PDF, Word and Image Annotation with GroupDocs Annotation
3. Online DOC, DOCX, PPT Document Comparison with GroupDocs Comparison
4. Online Document Management with GroupDocs Dashboard
5. Doc to PDF, Doc to Docx, PPT to PDF, and other Document Conversions with GroupDocs Viewer
6. Online Document Automation with GroupDocs Assembly