It seems that obj to pdo conversion is most likely used for purposes of import 3D objects (.obj) to Papekura Designer, so a new paper craft model design (.pdo) can be created from it. You can do this only using the original software and no other, as this particular pdo file type is only used by Papekura Designer.
Convert 3D object graphics to Pepakura Designer paper craft model design.
We have found one software suitable in our database for this conversion.
Microsoft Windows software - convert obj to pdo on Windows
A program used to create paper crafts from 3D data
Convert from obj file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.