OneSpan recommends against the use of XML Forms Architecture (XFA) in transaction PDFs. Instead, we recommend that you only use PDF documents that meet accepted ISO 32000-2 standards. For example, regular PDF 2.0, or PDF/A-2 documents. Using these formats ensures that our PDF processing will continue to meet the highest standards of quality and reliability.
XML Forms Architecture (XFA) is a set of XML specifications that was used in PDF files, beginning with the PDF 1.5 specification. However, XFA was never fully accepted as an ISO standard, and furthermore, XFA and all its related attributes were deprecated in the PDF 2.0 specification.
While OneSpan Sign never fully supported dynamic XFA files, it was possible to use a subset of static XFA documents, if certain conditions and settings were met (primarily in on-premises environments). However, with the deprecation of XFA specification support in PDF 2.0 the use of any type of static XFA documents is no longer recommended, and attempting to use such documents could result in inconsistent or even faulty UI behavior in a transaction's signed documents.
Note that these issues will not be detected when a transaction's PDF is validated.
As such, you should no longer use static XFA documents in your transactions and we recommend that existing XFA documents be transformed into standard PDF 2.0 documents.
We recommend that you transform your existing XFA documents to PDF/A documents. Converting XFA documents to PDF/A documents will resolve issues related to XFA fonts not being embedded (and subsetted) into your transformed PDFs.