Converting PDF to DWG file - similar question

I know this is similar to another question currently being posted, but I think the problem is different. I am downloading some pdf details into AutoCad and then overwriting on top of them so that I can make my own copies and make modifications. Everything has been going fine, but today, I have come across a couple pdf drawings that when I bring them into AutoCAD, the only thing that shows up is the border and the text. The lines defining the objects are not there. There are no layers identifed as turned off. Does anyone have any idea what is happening and how to correct it?

Have you tried using a different background colour in AutoCAD? We had a similar problem with black lines on a black background, couln't see a thing but the lines were there. We changed to a mid grey to be able to see the lines. That could be problematic if your PDF is in greyscale and not either black and white or colour.

Thanks for the suggestion. I confess that I do not know how to change the background color of my AutoCAD screen when I am editing/creating a drawing. I do not think that the background color is the issue though. I have scores of drawings from the same company and this has not been an issue on any of them. I will keep fooling around ot see if I can figure out if it is an issue with my background color though.

To change the background color go to Options > Display > Colors. At the Drawing Window Colors dialog box you'll see a headings for Context, Interface element and Color. Your choices should be 2D model space, uniform background, and black. Change the color setting to white, click on Apply & Close button then the OK button at the next window. You should now have a white background.

I know of a lisp routine that will do this from the keyboard.

Here's an option, clunky though it may be. Open the PDF in Acrobat. Export the detail as a JPG. Attach the JPG to your drawing instead of the PDF. If you don't have Acrobat but do have Adobe Reader, you can copy the document to the clipboard and paste it into your favorite graphics editor.

I've seen this before with PDFs. Apparently AutoCAD consolidates some pixels when it attaches graphics files, and in some cases the pixels you want can disappear entirely. You might try increasing the scale of the attached PDF--you can always shrink the detail later.