Some times you want to use a vector graphic compiled into a PDF file. Mose of us create a screenshot of the image and use it. But if the PDF drawing is a nice vector graphic, converting it to a bitmap is nothing you really want, do you?
So there is Inkscape which does a really good job importing PDF files – but in some cases it fails. This happens especially if there are some strange fonts in the PDF (which is often the case in pdflatex generated files).
A nice litte tool lets you to “screenshots” of PDF files while keeping all the vector graphics and fonts as they are: gpdfx
If you want to import the image into LibreOffice it is possible to convert the PDF to SVG, use pdf2svg (install in ubuntu). The resulting svg file is rahter big and not really good to edit, but the image looks exactly like in the PDF!