I've been using Zathura for quite a long time now. Lack of support of Russian, in my case, is a little bit disappointing. It is said in zathura issue #693 that girara "fails to handle non-ascii keys". I tried using Emacs for viewing pdfs but zathura is what I'm now used to.

So I added Russian symbols to callbacks.c where numpad keys are mapped to numbers row keys (line 42 and further):

  switch (*keyval) {
    ...
    case GDK_KEY_KP_9:
      *keyval = GDK_KEY_9;
      break;
    case GDK_KEY_Cyrillic_shorti:
      *keyval = GDK_KEY_q;
      break;
    case GDK_KEY_Cyrillic_SHORTI:
      *keyval = GDK_KEY_Q;
      break;
    ...
  }

It actually seems to work just like in Vim, where the letters work fine, but some punctuation marks have to be used based on active keyboard layout. I think this can also work with umlauts and other symbols not present on english keyboards. Would love to see something like this implemented.