Q:
We have files that use a Rijndael SHA256 encryption algorithm. Will PDFNet SDK work for us?
A:
If your document can be opened by Acrobat, then out-of-the-box PDFNet can open it. If not, you could enable PDFNet to open the document using a custom security handler.
That’s because we support all standard PDF encryption algorithms, but can also support custom encryption schemes (as shown in the sample code at https://www.pdftron.com/pdfnet/samplecode.html#EncTest). So if PDFNet’s built-in encryption is unsatisfactory for any reason, you can add support for another algorithm.
Regarding Rijndael SHA256 specifically — if you use PDFNet’s built-in 256 AES (i.e., Rijndael) encryption, it will compute SHA256 hashes of the password (as specified by http://wwwimages.adobe.com/content/dam/Adobe/en/devnet/pdf/pdfs/adobe_supplement_iso32000.pdf, Algorithm 3.2a).