transcoding noun [ U ]
the process of changing computer information that is stored in a particular code (= a language used to program computers) into another code:
The software provides "transcoding" - translation between standard web pages written in standard HTML (Hypertext Markup Language) and Wap's WML (Wireless Markup Language).
This feels the most correct term in this case. However my first thought was "port", which https://dictionary.cambridge.org/us/dictionary/english/port defines:
port verb [ T ]
to move software, a phone number, etc. to another system, without it being changed:
port sth to sth Our staff will check if your number can be ported to another
operator who will help you with the process.
So you could say:
The online forms are processed on a centralized platform without any transcoding.
The online forms are processed on a centralized platform without any porting.
Both of these are somewhat jargonistic, and in casual speech or writing you might instead consider are transcription, transferal (transferral in BrEng), re-encoding, interpretation or reinterpretation.
Other solutions would be to use a phrase instead of a word, such as requiring any change of media, transferal to another media, the need to export it to external formats etc.
However, you could instead change the sentence to remove the negative:
The online forms are stored, processed and reviewed end-to-end on a single, centralized platform. We use custom and bespoke file formats throughout, to ensure the highest quality vendor lock-in.
OK, maybe skip the second sentence, it's a bit too honest... but that seems to be closer to the intent of the sentence: to say that handling of the form does not require converting it to PDF, sending it via email, and other such hoop-jumping.