Convert PDB to STOCKHOLM

I saw a request on biostars: https://www.biostars.org/p/109442/
And tried to do it in UGENE: "Read Sequence > File Format Conversion".
The result was "The formats are not compatible: pdb and stockholm".

Apparently, such conversion makes sense, so it should be added to UGENE.
Also, take into account the details of the request:

The goal is to gain a sequence with information of missing residues. Tool shoud be insensitive to errors in PDB numberings or insertion codes or alternate locations.