I booked two separate envelopes of documents to be sent between EU countries with DHL. This should not incur any customs fees, charges or VAT. I stated on the paperwork, and also when asked by the customer support team before the labels were created, that it was documents only. I even wrote documents only on the parcel.
Unfortunately despite this, ParcelABC mistakenly booked both parcels with DHL under a code which indicated that there was tax to pay on the parcels (this was confirmed to me by DHL). So both parcels were held up by DHL, and the recipients had to pay an extra €30 each in DHL fees to receive the docs. The invoice on the DHL site shows that there was no VAT or duties due, but DHL charges for them handling the supposed duties, because of the code ParcelABC used.
And the ParcelABC support provided zero assistance. They said the paperwork was "with the courier" but the charges were never cancelled, so in the end the recipients paid the fees to get the documents.
EDIT: After the response from ParcelABC, I want to clarify that the customer support did reply several times, but when I say zero support I mean they were not helpful. For example, they said that they were checking with the courier, and then when I followed up a few days later they told me one of the packages had been delivered, which was clearly untrue. I had to ask them to re-read the same message thread below. So, I did get responses, but I was not impressed by them and they did not solve the problem in a timely manner.