Type Default Value Read Only Description

[Visual Basic]
true No Whether the viewer should automatically regenerate field appearances.




This property determines if the NeedAppearances flag in the PDF is set when field values are changed.

The NeedAppearances flag signals to the viewing application that field appearances should be automatically generated rather than using the appearance embedded in the PDF.

It is generally best to allow the viewing application to generate its own appearances and use the pre-generated ones as a fallback.

In PDF 2.0 the 'true' setting for this property has been deprecated. The logic is that documents should generate their own appearance streams rather than relying on the behavior of the viewer. There is truth in this, but also a problem - the generation of appearance streams is not defined in the specification - it inevitably varies between applications.

So the reality is that, without this flag, users may see a document which looks subtly different from the one they expect. We leave this default as true so that users see the documents as they expect. If you require strict adherence to PDF 2.0 then you may wish to set it to false.