How to Check PDF is Reader enabled or not using C#?

Question

My only requirement is to find a selected pdf in a folder is Reader enabled or not, more specifically if usage rights are defined in a way that allows people to add annotations (e.g. comments).

I am doing this in windows application. If I click a button, an event is triggered searching a folder for PDF files. This event needs to check whether or not the PDFs in the folder are Reader enabled for comments. If they are, I need to remove the comment usage rights or revert the PDF back to its original version.

My code can only find PDF files in the folder. I don`t know how to check if the selected PDF is comment enabled or not. Please be gentle and suggest solution.

Here's my code:

private void button1_Click(object sender, EventArgs e)
{
    {
        string[] filePaths = Directory.GetFiles("D:\\myfolder\\pdffolder");
        List<ListViewItem> files = new List<ListViewItem>();
        foreach (string filePath in filePaths)
        {
            ---need to check comment enabled or not---
        }
    }
}

Answer 1

You want to know if a PDF is Reader enabled or not. Reader enabling is established by adding a digital signature known as a Usage Rights (UR) signature. If you have an instance of PdfReader, you can check whether or not a PDF is Reader enabled by using the hasUsageRights() method:

PdfReader reader = new PdfReader(path_to_file);
boolean isReaderEnabled = reader.hasUsageRights();

Usage rights can encompass many different things, such as allowing people to comment, allowing people to save a filled out form, allowing people to sign a document,...

To find out which rights are enabled, you have to inspect either the UR or the UR3 dictionary (note that UR is deprecated, but there may still be PDFs out there that have a UR dictionary):

PdfDictionary catalog = reader.getCatalog();
PdfDictionary perms = catalog.getAsDict(PdfName.PERMS);
PdfDictionary ur = null;
if (perms != null) {
    PdfDictionary ur = perms.getAsDict(PdfName.UR);
    if (ur == null)
        ur = perms.getAsDict(PdfName.UR3);
    }
}

If ur remains null, there are no usage rights. If you only want to check if commenting is enabled, you'll have to inspect the entries of the ur dictionary. There will be an /Annots entry with as value an array with values such as Create, Delete, Modify, Copy, Import, Export, Online and SummaryView. FOr the full overview of possible entries, see Table 255 "Entries in the UR transform parameters dictionary" of ISO-32000-1.

You can remove all usage rights like this:

PdfReader reader = new PdfReader(path_to_file);
if (reader.hasUsageRights()) {
    reader.removeUsageRights();
    PdfStamper stamper = new PdfStamper(reader, new FileOutputStream(path_to_new_file));
    stamper.close();
}

It is impossible to remove only the usage rights for commenting while preserving other usage rights (if present). Just removing the /Annots entry from the /UR or /UR3 dictionary will break the digital signature that enables usage rights. This digital signature is created with a private key owned by Adobe and no third party tool (other than an Adobe product) is allowed to use that key.

Final note:

all code snippet were written in Java, but iTextSharp has corresponding methods or properties in C#. It shouldn't be a problem to port the snippets to C#.

In many cases, it's sufficient to change a lower case into an upper case:

• Java: object.add(something);
• C#: object.Add(something);

Or you have to remove the set/get:

• Java: object.setSomething(something);
• C#: object.Something = something;

Answer 2

Thanks for all who takes effect to my question. I finally found the answer in a similar way by reading the PDF and check for a particular string (particular string presented if Comment enabled on the PDF).

The particular string starts with /Annot ....., First I read the PDF thru System.IO, then store in a string and looking for the particular string, If the searching string available then the PDF is comment enabled else not.