You cannot import symbols directly from a PDF into EFD. There are two ways to copy a symbol from a PDF, but both bring it into EFD as an image, not a proper EFD symbol.
TIP: For either method, it is best to use the logo converter first to resize and crop the image. Insert a Logo Using Copy and Paste explains how to use the converter and paste the image into EFD.
Use the Windows Snipping Tool
Reduce the zoom level in your PDF before clipping the symbol. Use the Windows Snipping Tool to select an area around it. This copies the selection to the clipboard, ready to paste into EFD as an image.
NOTE: Clipping a symbol while it looks large on screen produces a large image. This increases the size of your EFD file and could cause issues on Floorplan Live if you use many of these images.
Copy an existing image using Adobe tools
If the symbol inside the PDF is already an image, use the Adobe tools to select and copy it, then paste it into EFD.
Check the image size after pasting it into EFD to make sure it is not too large.
Creating a proper EFD symbol
These methods insert images rather than proper EFD symbols. Proper symbols are made using MODIFY > BUILD > Build Symbol. See Create a Symbol.