On one occasion I had to use ZAMZAR to edit a pdf file (on line) and now all my pdf files are opening in Libreoffice Draw.
My o.s. is Ubuntu 15.10 and my Libreoffice Writer is ver 15.0.1.6.
I have read answers to similar questions but, unfortunately, I have not found any of them helpful.
You told a story about your past, but you didn’t explain what is the problem that you want to solve actually. I suppose that it’s “I want that PDFs be opened with ZAMZAR instead of Draw, how to do that?”, but that’s just my guess 
I want all my files to open on Libreoffice Writer, like they always did.
For the rare occasion of a pdf file, I shall have to find a pdf reader/writer.
Reset the file associations so that LO has all its default files (.odt, .ods, .doc, .docx etc). In Windows it is Start > Control Panel > Default Programs. It will be something similar in Ubuntu.
If this helps then please tick the answer and/or show you like it with an uptick.
Thanks but this is beyond me! I will look into it when my “brain box” starts function like it used to when I was younger. I shall need a quiet moment; a rare thing for me these days. Thanks again.
I have clicked on a pdf file at random and set it to open with Libreoffice Writer, made this the default program for all pdf files, but the problem still persists.
I have a feeling the problem came when I attempted to edit a pdf file on line, because, ever since then, my pdf reader is showing what seems like a sub menu called vindeloo. I have never downloaded, or installed, or even heard of vindeloo. Perhaps I should find a way to remove vindeloo somehow?
Thanks again.