There are two ways you can convert the .odt (document) file into pdf format.
a) Open the document in Open Office Writer (Word); then when it is already opened click 'File' >> 'Export as PDF' >> a window will open for you to make particular specifications to the new pdf file, if you don't need to specify anything click 'Export', write the file name and select folder, then finally click 'Export'. After doing doing that process you can go to the folder where you saved it, try open it is already in PDF.
Another way is to--
b) Open the document then click 'Print', in the printer dialogue box highlight radio button 'Print to File' (it is just below the Comment), then save it into a folder. If you are lucky there is a choice for Pdf, but usually it comes in a ghostscript format, just similar to pdf.
Hope this helps. Good luck.