It appears that both .dpl and .ddl files are used by Ovation Pro desktop publishing program and some sort of conversion or export may be possible with the original tool. Sadly, we could not reliably verify this information and thus the viability of dpd to ddl conversion remains uncertain.
Updated: January 23, 2017
This conversion entry was verified by us and conversion was flagged as wrong or not possible.
Usually this happens when the conversion would try to convert different types of data between each other, such as audio to image, or it is not possible because incompatibility between programs, caused by closed file formats, very limited support etc.
If you find entry that you feel is flagged as bad wrongly, please tell us in the discussion below with as much as information as possible so we can fix it.