Hi Paul.
PDF conversion is available in Professional subscription of HTML5 Flipping Book.
To convert a pdf to a publication, go to Management > Pages and click 'Convert from PDF' (here's the screenshot
gyazo.com/c30a66c95218f8dcb2f164bf30672070).
The pages of this pdf file will be automatically converted with the help of ImageMagick and will be stored as images in the component's folder.
PDF files will be converted to publications regardless of their size. But we do not recommend to create flipping books with more than a hundred pages, as they may load slower. You can test it on your site, it depends on many other reasons as well, so it may load normally even with 200 pages.
Best regards.