Hash that works with:
cudaHashcat64 -m 10500 -a 3 PDF-password-is-hashcat.hash ?l?l?l?l?l?l?l

PDF-password-is-hashcat.hash
----------------------------
$pdf$2*3*128*-1028*1*16*da42ee15d4b3e08fe5b9ecea0e02ad0f*32*c9b59d72c7c670c42eeb4fca1d2ca15000000000000000000000000000000000*32*c4ff3e868dc87604626c2b8c259297a14d58c6309c70b00afdfb1fbba10ee571

Hash that doesn't work:
cudaHashcat64 -m 10500 -a 3 PDF-password-is-...hash ?b?b

PDF-password-is-...hash
-----------------------
$pdf$4*4*128*-1324*1*32*e85bab525883d8493ece960c6038dcdcc75a428632fd4e45ba43bfe17ec3adc5*32*f9ce566a10eba70977b1b24f23d0861c00000000000000000000000000000000*32*00e5507dabd18be0aa0d9f4c70607c0fa183ba9cf5e503026a524319b5e775f8