The PDF file format predates the web and was never designed for simple conversion into web pages. So, when converting a PDF file into HTML5 content, there are different ways to go about it depending on your priorities. HTML5 contains different features compared to PDF, so there is not always a direct match.
For example, the PDF file format allows individual control over the spacing between each text character. You can emulate this in HTML5 by putting each character in its own div tag but this can create large files. So in this case is an exact layout or smaller filesize more important to you?
Option 1. Make an image of the page
Display as an image element in HTML5
Advantages: Simple. Looks identical.
Disadvantages: Large file size, does not scale, text not selectable.
Option 2. Make a image of the page and get text
Display as an image in HTML5 with hidden text behind it to allow text selection and search
Advantages: looks identical and gives text selection.
Disadvantages: Large file size, does not scale, text may be ignored by search engines.
Option 3. Convert all Contents into HTML5 equivalent
Advantages: Text stays as text, images stay as images and Vector content can be put on canvas or image. Smaller file size, perfect zoom on text, searchable.
Disadvantages: PDF layout not exactly reproducible, lots of work with font conversions. Can you legally use the fonts?
Option 4. Convert content into SVG
Advantages: SVG often looks better than HTML5 for text and images. All modern browsers can display SVG
Disadvantages: SVG does not offer key HTML5 features like forms.
In practice we find that a combination of the above is the best general case (with the option to use other modes if more appropriate).
Where can I see some examples?