Multiple things you can done to lower an HelpNDoc project file size:
- Make sure you delete any un-needed library item (pictures, videos...). The project analyzer can help you locate them. See: How to analyze the items in your library;
- Make sure that you merge duplicate library items into a single item. Once again, the project analyzer will help you locate and merge items;
- Consider using compressed picture formats in your library: prefer the PNG or JPEG formats over uncompressed BMP... formats;
- Do not embed videos in your project: prefer online video hosts such as YouTube or Vimeo;
- Once all the above is done, from HelpNDoc's "Tools" ribbon tab, click the "Vacuum project" button to clean any unused space in your HND project file.