Add digital signature or digitally sign PDF in Python

Sign PDF with digital signatures

    import aspose.pdf as ap
    import aspose.pydrawing as drawing

    ppath_infile = self.data_dir + infile
    path_outfile = self.data_dir + outfile
    path_pfxfile = self.data_dir + pfxfile

    # Open PDF document
    with ap.Document(path_infile) as document:
        # Instantiate PdfFileSignature object
        with ap.facades.PdfFileSignature(document) as signature:
            # Create PKCS#7 object for sign
            pkcs = ap.forms.PKCS7(path_pfxfile, "12345")
            # Sign PDF file
            signature.sign(1, True, drawing.Rectangle(300, 100, 400, 200), pkcs)
            #  Save PDF document
            signature.save(path_outfile)

A PKCS#7 detached signature adds a digital signature to a document without embedding the content into the signature block.

The next example signs a PDF document using a PKCS#7 detached digital signature, applying the signature to the first page in a specified rectangular area.

    import aspose.pdf as ap
    import aspose.pydrawing as drawing

    path_infile = self.data_dir + infile
    path_outfile = self.data_dir + outfile
    path_pfxfile = self.data_dir + pfxfile

    # Open PDF document
    with ap.Document(path_infile) as document:
        # Instantiate PdfFileSignature object using the opened document
        with ap.facades.PdfFileSignature(document) as signature:
            # Create PKCS#7 detached object for sign
            pkcs = ap.forms.PKCS7Detached(path_pfxfile, password, ap.DigestHashAlgorithm.SHA256)
            # Sign PDF file
            signature.sign(1, True, drawing.Rectangle(300, 100, 400, 200), pkcs)
            #  Save PDF document
            signature.save(path_outfile)

This Python code snippet verifies a digital signature in a PDF file using ‘file_sign.verify_signature()’ method.

1. Creates an instance of PdfFileSignature that allows you to interact with signatures in PDF.
2. Get a list of signature names get_signature_names(True).
3. Checks the first signature in the list verify_signature for compliance with the specified certificate.

    import aspose.pdf as ap

    path_infile = self.data_dir + infile

    # Create an instance of PdfFileSignature for working with signatures in the document
    with ap.facades.PdfFileSignature(path_infile) as file_sign:
        # Get a list of signatures
        signature_names = file_sign.get_signature_names(True)
        # Verify the signature with the given name.
        return file_sign.verify_signature(signature_names[0], certificate)

Add timestamp to digital signature

How to digitally sign a PDF with timestamp

Aspose.PDF for Python supports to digitally sign the PDF with a timestamp server or Web service.

In order to accomplish this requirement, the TimestampSettings class has been added to the Aspose.PDF namespace. Please take a look at the following code snippet which obtains timestamp and adds it to PDF document:

    import aspose.pdf as ap
    import aspose.pydrawing as drawing

    path_infile = self.data_dir + infile
    path_outfile = self.data_dir + outfile
    path_pfxfile = self.data_dir + pfxfile

    # Open PDF document
    with ap.Document(path_infile) as document:
        # Create an instance of PdfFileSignature for working with signatures in the document
        with ap.facades.PdfFileSignature(document) as signature:
            pkcs = ap.forms.PKCS7(path_pfxfile, password)
            # Create TimestampSettings settings
            timestamp_settings = ap.TimestampSettings("https://freetsa.org/tsr",
                                                                "", ap.DigestHashAlgorithm.SHA256)  # User/Password can be omitted
            pkcs.timestamp_settings = timestamp_settings
            rect = drawing.Rectangle(100, 100, 200, 100)  # Creating a rectangle for the signature
            # Create any of the three signature types
            signature.sign(1, "Signature Reason", "Contact", "Location", True, rect, pkcs)
            # Save PDF document
                signature.save(path_outfile)

Signing PDF documents using ECDSA

Signing PDF documents using ECDSA (Elliptic Curve Digital Signature Algorithm) involves utilizing elliptic curve cryptography to generate digital signatures.

The code snippet above illustrates how to apply a PKCS#7 detached digital signature to a PDF document using Aspose.PDF for Python. By loading the document, configuring the signature appearance and security settings, and saving the result, this example demonstrates a complete, reliable workflow for digitally signing PDF files.

This method ensures the document’s authenticity and integrity by embedding a secure, verifiable signature on the first page. The use of SHA-256 as the digest algorithm meets modern cryptographic standards, while the ability to control signature placement offers flexibility for visible approval marks.

    import aspose.pdf as ap
    import aspose.pydrawing as drawing

    path_infile = self.data_dir + infile
    path_outfile = self.data_dir + outfile
    path_pfxfile = self.data_dir + pfxfile

    # Open PDF document
    with ap.Document(path_infile) as document:
        # Create an instance of PdfFileSignature to sign the document
        with ap.facades.PdfFileSignature(document) as signature:
            # Create a PKCS7Detached object using the provided certificate and password
            pkcs = ap.forms.PKCS7Detached(path_pfxfile, password, ap.DigestHashAlgorithm.SHA256)

            # Sign the first page of the document, setting the signature's appearance at the specified location
            signature.sign(1, True, drawing.Rectangle(300, 100, 400, 200), pkcs)

            # Save PDF document
            signature.save(path_outfile)