I received a pdf document consisting of a series of color drawings for editing and translation.
Usually I copy the drawings from the pdf files and convert them into gif format, and load them into MSWord for editing and text addition.
However in the recent document Word does not accept the gif drawings. I tried to convert them into jpg and in this format all is OK, but I prefer to work with gif.
What can be done, and why Word doesn’t accept GIF?

Just Googling here as a first response:

I find this one issue regarding transparency in the creation:

But I might have a theory. I've noticed that whenever I wanted to convert, let say a picture or a document, it does the compressing conversation before actually writing to PDF format. And I also noticed that it converts to JPG format. So essentially the PDF you created is nothing more than series of JPG pictures scrolling like a document. Well, when transparent GIF is converted to JPG we all know that the transparency cannot be preserved. JPG does not support transparent background.

Transparent Gif's In Word Or Pdf Document - Open Discussion

Anyway as said just a quick first response.