How can I find out whether a PDF has embedded thumbnails?

[Aaron]

Q:  How can I check whether my document has embedded thumbails?

A:

The easiest way to investigate whether a PDF has thumbs is to open it in CosEdit (https://www.pdftron.com/pdfcosedit/downloads.html), then traverse to any page (e.g., the first page at trailer/Root/Pages/Kids/0) and look for a stream named Thumb (which should be an image).  That image stream is the page's embedded thumbnail.

If you'd prefer to test for this programmatically, you can do so using Page.GetThumb:

https://www.pdftron.com/pdfnet/docs/PDFNet/html/M_pdftron_PDF_Page_GetThumb.htm