Greetings!

So I have some pub files that I'm needing to edit on my Ubuntu PC. Currently I have no idea on how to go about editing them. Gimp can open them and allow me to do any editing I wish but are obviously unable to save back into a pub or pdf format. 'Libreoffice impress' seems to be the eqivilent of Microsoft publisher but when I try and open the file with it, it shows a window entitled 'filter selection' which I have no idea what to do with. I did convert the troublesome pub file to a pdf but when opening with libreoffice impress it just showed lots of weired characters. How can I go about editing pub files?

Thanks bye!