PDF JS - Lazy load?

Question

It seems, pdf.js itself requesting whole byte range requests of a PDF file. Instead, is it possible to request only 5 pages on PDF load, On scroll can able to load another set of 5 pages, like that.. Is there a way to achieve this by using pdf.js ?

Answer 1

Long story short - No.

PDF is not a contiguous storage format. If the PDF file is formatted for fast web view then you can get it to show page 1 whilst other pages are still streaming in, but you can't ask to start at a specific page or page range. Internally pdf uses a bunch of sections, links/pointers between them and digests. Think of them as wooden blocks with bits of string between them. You can't render anything until you have 'enough' of the file to provide the parts you need, but the organisation of the internal sections is pretty much random as far as your question is concerned.

The only way to get specific pages would be to have a server-side component split them out of the PDF file for you and make a new PDF file containing just those parts, but paging on to page 6 would mean opening a new document, etc.

Edit: There are startup params for Acrobat viewer that could allow you to set the first page to be displayed, and other viewers may offer this feature, but unless you have some very smart client-server interaction this would still require the entire PDF document to be present in the client first.

Edit 2: As per comment from @async5, PDF.js 'may' be able to do page-range loading. See this section of the PDF.js docs. But note that there are requirements on the web server that is serving the PDF file.