Q:
just wondering if there is any functionality to extract/filter the spot color or die lines in pdf’s?
A:
Are you are talking about page content surrounding the page (typically outside of the crop box)?
In this case you could use element positioning information (element.GetBBox()) to determine if the element is inside or outside of the crop box (page.GetCropBox()).
For example of how to filter out content (i.e. edit the page) please see ElementEdit sample.
If you want to find a list of spot colorants used on a given page please see:
https://groups.google.com/d/topic/pdfnet-sdk/t3HGr9lrfRc/discussion