Via this intermediate link?

[GalcoIndustrial]

I'm doing some work on an ecommerce site for an electronics distributor and I've been seeing these "Via this intermediate link" notations from GWT under our "Links To Your Site" section.  I understand how and why these notations would normally be displayed, however, these links are mainly coming from our direct competitors.  Fearing that we might be a victim of a negative SEO attack, I looked into the situation and noticed that all of the links are from PDF's (technical data sheets) provided by the manufacturer that both we and our competitors use on our product detail pages.  This still seems odd to me because, we download these pdf's and host them on our own site on our own servers under a completely different name (as I'm assuming our competitors do as well), yet, there still seems to be a connection between our sites through these PDF's.

I've included a screenshot of some examples.  Since we have thousands of SKU's on our site - with technical PDF's for nearly all of them - we're seeing a lot of links from competitors sites.  I'm not sure if this is good or bad, I'm just trying to understand the situation more clearly.

Has anyone had any similar experiences or some information from Google that might explain what I'm seeing here?

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[RyanPurkey]

HI Gerard. I think what you're seeing is the redirect on your own site. See the discussion here: https://productforums.google.com/forum/#!topic/webmasters/mGA6ygCUtWE, noting this part of the thread, "someblog.com/post-1 links to mysite.com/page1, however mysite.com/page1 redirects to mysite.com/otherpage".

Maybe your competitors just linked to your hosting of the PDF instead of downloading and hosting their own.