I'm putting together a drawing and I'm trying to paste in an image I captured with Snipping Tool from a PDF. When I paste the picture in, sometimes the white background is removed and it is just the text and lines on a transparent background. This looks really nice and I want all the picture to be like this but sometimes it pastes it in with a white background. I cannot figure out if it's Acrobat Pro, Snipping Tool, or Solidworks that's deleting the background but I'm leaning towards SW. What is causing this feature and how can I enable it always? Anyone else experienced this before?

Attached is a picture of what I'm talking about. I put the image on the edge of the page and you can see that the background of the image is transparent.

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Thanks.