Acrobat restriction

Question

I want to add some function to manipulate PDF file such as creating or editing annotation. I searched the web and found one forum to indicated that there are acrobat-forms which check itself if they are modified by third party tools and if it's so then you can't show the pdf via adobe reader. The forum was posted on April in 2010. Is it still same?

Answer 1

Your forum is correct. However things are changing over time so the particular restrictions in place are not constant.

Some features would be very useful in a PDF but Adobe define them as "Extended Features". This means that they are enabled in Acrobat Reader but only if the PDF was created using Acrobat Pro.

This means that Adobe can continue to provide a free reader but at the same time encourage people to purchase Acrobat Pro since only it can be used to create this type of document.

The way this is detected is via a digital signature inserted into the PDF. If the signature is not present or has been invalidated by modifying the document then you will see a message along these lines.

“This document enabled extended features in Adobe Reader. The document has been changed since it was created and use of extended features is no longer available. Please contact the author for the original version of this document.”

In the past the key extended feature which was restricted this way was the ability to save changes to forms and fields. However as of the release of Acrobat Reader XI this is no longer the case.

Acrobat Reader XI provides features to save eForms out of the box. Provided you are using this version of Acrobat you will be able to fill in and save standard PDF forms. The only problem you may have relates to older versions of Acrobat Reader which did not have this feature.

There are other extended features which can be similarly made specific to a particular PDF created by a particular tool. No doubt these will change over time as the market evolves..

In theory it is possible to license Adobe's digital certificate so you can create similar documents. We (at ABCpdf .NET) attempted to do this some years ago but without success. I believe that SAP is the only company ever to have done this.

I think that would have to be classified as the definitive answer. Even if I do say so myself. ;-)