De or het douanedocument?

The correct Dutch article is:

het douanedocument

Rule Words ending in -ment: usually het. See the rule

How to use douanedocument

the douanedocumenthet douanedocument
this douanedocumentdit douanedocument
that douanedocumentdat douanedocument
our douanedocumentons douanedocument
your douanedocumentjouw douanedocument
every douanedocumentelk douanedocument
which douanedocument?welk douanedocument?
a big douanedocument / the big douanedocumenteen groot douanedocument, het grote douanedocument