I am using Adobe Acrobat Pro 2015.006.30121 in Windows 10.
I need to submit documents with my digital signature to a court. The court uses a program that requires the document to be PDF Version of 1.5 or lower. I save my pdf document using File/Save As Other/Reduced Size PDF. When I look at File/Properties/Document Properties Description the PDF Version is 1.5. However, after I apply my Acrobat digital signature the PDF Version is increased to 1.6. Now the document is uneditable so I cannot do another File/Save As Other to reduce the PDF Version back to 1.5. How do I change a setting such that applying my digital signature does NOT increase the PDF Version?
The features that you need to apply your digital signature do not exist in PDF 1.5. That's why Acrobat increases the version number to match the features it needs. I do not remember which exactly features were introduced in 1.6. I think that SHA2 hash and AES encryption were among the, So, for instance, if your signing certificate uses SHA2 (SHA-256) hash the created signature cannot be opened with 1.5 PDF Viewer. I am not saying that this happen in your case. This just an example of what might've happened.