How get acrofield custom attributes with iTextSharp

Question

I have a PDF (vs1 (dopo).pdf) with 6 acrofield ... 4 radio button and 2 signature fields. Signature fields have some custom properties that I would like to read but I don't know how. This is the code I use to retrieve the fields:

PdfReader pdfReader = new PdfReader (inputPDFPath);
AcroFields pdfFormFields = pdfReader.AcroFields;
            
foreach (KeyValuePair <string, AcroFields.Item> kvp in pdfFormFields.Fields)
{
     string fieldName = kvp.Key.ToString ();
     string fieldValue = pdfFormFields.GetField (kvp.Key.ToString ());
     Console.WriteLine (fieldName + "" + fieldValue);
}

pdfReader.Close ();

Signature fields have these properties:

kvp.Value.GetValue(0).Keys

[Count = 12
    [0]: {/F}
    [1]: {/FT}
    [2]: {/Ff}
    [3]: {/MK}
    [4]: {/P}
    [5]: {/Rect}
    [6]: {/SSCbio}
    [7]: {/SSCreq}
    [8]: {/Subtype}
    [9]: {/T}
    [10]: {/sq}
    [11]: {/uid}]

How can I retrieve the value of {/uid}, {/SSCbio}, ...?

score 1 · Accepted Answer · answered Jun 23 '20 at 13:39

You inspected kvp.Value.GetValue(0).Keys, so you nearly already were there! kvp.Value.GetValue(0) is a PdfDictionary you can query the values of:

foreach (KeyValuePair<string, AcroFields.Item> kvp in pdfFormFields.Fields)
{
    string fieldName = kvp.Key.ToString();
    string fieldValue = pdfFormFields.GetField(kvp.Key.ToString());
    Console.WriteLine(fieldName + " - " + fieldValue);
    PdfDictionary merged = kvp.Value.GetValue(0);
    foreach (PdfName key in merged.Keys)
    {
        Console.WriteLine("    {0}: {1}", key, merged.GetDirectObject(key));
    }
}

For the signature fields this returns:

Firme statiche (1) - 
    /F: 4
    /FT: /Sig
    /Ff: 0
    /MK: Dictionary
    /P: Dictionary of type: /Page
    /Rect: [392.4, 125.016, 505.632, 153.324]
    /SSCbio: 1
    /SSCreq: 1
    /Subtype: /Widget
    /T: Firme statiche (1)
    /sq: -1
    /uid: Firme statiche
Firme statiche (2) - 
    /F: 4
    /FT: /Sig
    /Ff: 0
    /MK: Dictionary
    /P: Dictionary of type: /Page
    /Rect: [231.12, 87.576, 301.89, 115.884]
    /SSCbio: 1
    /SSCreq: 1
    /Subtype: /Widget
    /T: Firme statiche (2)
    /sq: -1
    /uid: Firme statiche

As an aside, those keys SSCbio, SSCReq, sq, and uid are not defined by the PDF specification. Furthermore, they don't have a registered prefix and no developer extension is declared. Thus, those PDFs should be for internal use in your organisation only and never get out into the wild.

Also I hope you have established a process to check upon every PDF viewer / signer / validator update relevant in your organisation whether those additions still don't interfere with their operation...

Thanks a lot for the answer. The properties are exactly for internal use and inserted with a third party component (xyzmo). Now I would like to do the same thing with iTextSharp using `pdfStamper.AddAnnotation(sig, pageNumber);` where `PdfFormField sig = PdfFormField.CreateSignature(pdfStamper.Writer);` but how can I insert a custom key (eg: **/SSBio**, **/uid**, ...) in the `sig` object? — Gigi, Jun 23 '20 at 15:45
Found it! This is the code to add an arbitrary key (eg: **uid**) `PdfDictionary merged = new PdfDictionary(); merged.Put(new PdfName("uid"), new PdfString("my uid")); sig.Merge(merged);` — Gigi, Jun 24 '20 at 07:19

How get acrofield custom attributes with iTextSharp

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