Verifying digital signatures in a PDF is essential for ensuring the authenticity and integrity of electronically signed documents. It confirms that the signature is valid and that the document has not been altered since signing. Additionally, extracting signature images from a PDF allows you to retrieve and save the visual representation of a signature, making it easier to verify and archive for legal or record-keeping purposes. In this article, we will demonstrate how to verify and extract digital signatures in PDF in Python using Spire.PDF for Python.

• Verify Digital Signatures in PDF in Python
• Detect Whether a Signed PDF Has Been Modified in Python
• Extract Signature Images from PDF in Python

Install Spire.PDF for Python

This scenario requires Spire.PDF for Python and plum-dispatch v1.7.4. They can be easily installed in your Windows through the following pip command.

pip install Spire.PDF

If you are unsure how to install, please refer to this tutorial: How to Install Spire.PDF for Python on Windows

Verify Signatures in PDF in Python

Spire.PDF for Python provides the PdfDocument.VerifySignature(signName: str) method to check the validity of a digital signature in a PDF document. The detailed steps are as follows.

• Create an object of the PdfDocument class.
• Load a PDF file using the PdfDocument.LoadFromFile() method.
• Get the form of the PDF file using the PdfDocument.Form property.
• Iterate through all fields in the form and find the signature field.
• Get the name of the signature field using the PdfSignatureFieldWidget.FullName property.
• Verify the validity of the signature using the PdfSignature.VerifySignature(signName: str) method.

from spire.pdf.common import *
from spire.pdf import *

# Load a PDF document
doc = PdfDocument()
doc.LoadFromFile("Signature.pdf")

# Access the form in the document
pdfform = doc.Form
formWidget = PdfFormWidget(pdfform)

# Check if there are any fields in the form
if formWidget.FieldsWidget.Count > 0:
        # Loop through all fields in the form
        for i in range(formWidget.FieldsWidget.Count):
            field = formWidget.FieldsWidget.get_Item(i)

            # Check if the field is a PdfSignatureFieldWidget
            if isinstance(field, PdfSignatureFieldWidget):
                # Typecast the field to a PdfSignatureFieldWidget instance
                signatureField = PdfSignatureFieldWidget(field)
                # Get the name of the signature field
                fullName = signatureField.FullName

                # Verify the signature
                valid = doc.VerifySignature(fullName)
                # Determine the validation status text based on the verification result
                if valid:
                    print("The signature is valid")
                else:
                    print("The signature is invalid")

doc.Close()

Detect Whether a Signed PDF Has Been Modified in Python

To determine whether a PDF document has been modified after signing, use the Security_PdfSignature.VerifyDocModified() method. This method returns a Boolean value: True indicates that the document has been altered and the signature is no longer valid, while False confirms that the document remains unchanged since it was signed. The detailed steps are as follows.

• Create an object of the PdfDocument class.
• Load a PDF file using the PdfDocument.LoadFromFile() method.
• Get the form of the PDF file using the PdfDocument.Form property.
• Iterate through all fields in the form and find the signature field.
• Get the signature using the PdfSignatureFieldWidget.Signature property.
• Verify if the document has been modified since it was signed using the Security_PdfSignature.VerifyDocModified() method.

from spire.pdf.common import *
from spire.pdf import *

# Load a PDF document
doc = PdfDocument()
doc.LoadFromFile("Signature.pdf")

# Access the form in the document
pdfform = doc.Form
formWidget = PdfFormWidget(pdfform)

# Check if there are any fields in the form
if formWidget.FieldsWidget.Count > 0:
        # Loop through all fields in the form
        for i in range(formWidget.FieldsWidget.Count):
            field = formWidget.FieldsWidget.get_Item(i)

            # Check if the field is a PdfSignatureFieldWidget
            if isinstance(field, PdfSignatureFieldWidget):
                # Typecast the field to a PdfSignatureFieldWidget instance
                signatureField = PdfSignatureFieldWidget(field)

                # Get the signature
                signature = signatureField.Signature
                # Verify if the document has been modified since it was signed 
                modified = signature.VerifyDocModified()
            
                # Determine the validation status text based on the verification result
                if modified:
                    print("The document has been modified")
                else:
                    print("The document has not been modified")

doc.Close()

Extract Signature Images from PDF in Python

Spire.PDF for Python allows extracting all signature images from a PDF document using the PdfFormWidget.ExtractSignatureAsImages property. The detailed steps are as follows.

• Create an object of the PdfDocument class.
• Load a PDF file using the PdfDocument.LoadFromFile() method.
• Get the form of the PDF file using the PdfDocument.Form property.
• Extract signature images from the form using the PdfFormWidget.ExtractSignatureAsImages property.
• Save the extracted images to image files.

from spire.pdf.common import *
from spire.pdf import *

# Load a PDF document
doc = PdfDocument()
doc.LoadFromFile("Signature.pdf")

# Access the form in the document
pdfform = doc.Form
formWidget = PdfFormWidget(pdfform)

i = 0
# Extract signature images from the form and save them to files
for image in formWidget.ExtractSignatureAsImages:
    filename = "Signature/" + f"Image-{i}.png"
    # Save the image to a file
    image.Save(filename)
    i = i + 1

doc.Close()

Apply for a Temporary License

If you'd like to remove the evaluation message from the generated documents, or to get rid of the function limitations, please request a 30-day trial license for yourself.

The ability to set a password for a PDF document or remove the password from an encrypted PDF document is invaluable for securing sensitive information while maintaining the flexibility and convenience of working with PDF files. By setting up passwords for PDF documents, individuals can control access to their files, preventing unauthorized viewing, editing, or copying. Conversely, unprotecting a PDF document can make the document accessible or editable again. In this article, you will learn how to password-protect PDF documents as well as how to remove passwords from encrypt PDF documents using Spire.PDF for Python.

• Protect PDF with Password in Python
• Remove Password from an Encrypted PDF in Python

Install Spire.PDF for Python

This scenario requires Spire.PDF for Python and plum-dispatch v1.7.4. They can be easily installed in your Windows through the following pip command.

pip install Spire.PDF

If you are unsure how to install, please refer to this tutorial: How to Install Spire.PDF for Python on Windows

Protect PDF with Password in Python

There are two types of passwords that can be used for security purposes: the "open password" and the "permission password". An open password, also known as a user password, is used to restrict unauthorized access to a PDF file. A permission password, also referred to as a master password or owner password, allows you to set various restrictions on what others can do with the PDF file. If a PDF file is secured with both types of passwords, it can be opened with either password.

The PdfDocument.Security.Encrypt(String openPassword, String permissionPassword, PdfPermissionsFlags permissions, PdfEncryptionKeySize keySize) method offered by Spire.PDF for Python allows you to protect PDF files with an open password and/or a permission password. The parameter PdfPermessionsFlags is used to specify the user's permission to operate the document.

Here are the steps to password-protect a PDF with Spire.PDF for Python.

• Create a PdfDocument object.
• Load a sample PDF file using PdfDocument.LoadFromFile() method.
• Encrypt the PDF file with an open password and permission password using PdfDocument.Security.Encrypt(String openPassword, String permissionPassword, PdfPermissionsFlags permissions, PdfEncryptionKeySize keySize) method.
• Save the result file using PdfDocument.SaveToFile() method.

from spire.pdf.common import *
from spire.pdf import *

# Create a PdfDocument object
doc = PdfDocument()

# Load a sample PDF file
doc.LoadFromFile("C:/Users/Administrator/Desktop/input.pdf")

# Encrypt the PDF file with an open password and a permission password
doc.Security.Encrypt("openPsd", "permissionPsd", PdfPermissionsFlags.FillFields, PdfEncryptionKeySize.Key128Bit)

# Save the result file
doc.SaveToFile("output/Encrypted.pdf", FileFormat.PDF)

Remove Password from an Encrypted PDF in Python

To remove the password from a PDF file, call the PdfDocument.Security.Encrypt() method and leave the open password and permission password empty. The following are the detailed steps.

• Create a PdfDocument object.
• Load an encrypted PDF file using PdfDocument.LoadFromFile(String fileName, String password) method.
• Decrypt the PDF file by setting the open password and permission password to empty using PdfSecurity.Encrypt(String openPassword, String permissionPassword, PdfPermissionsFlags permissions, PdfEncryptionKeySize keySize, String originalPermissionPassword) method.
• Save the result file using PdfDocument.SaveToFile() method.

from spire.pdf.common import *
from spire.pdf import *

# Create a PdfDocument object
doc = PdfDocument()

# Load an encrypted PDF file
doc.LoadFromFile("C:/Users/Administrator/Desktop/Encrypted.pdf", "openPsd")

# Set the open password and permission password as empty 
doc.Security.Encrypt(str(), str(), PdfPermissionsFlags.Default, PdfEncryptionKeySize.Key128Bit, "permissionPsd")

# Save the result file
doc.SaveToFile("output/RemovePassword.pdf", FileFormat.PDF)

Apply for a Temporary License

If you'd like to remove the evaluation message from the generated documents, or to get rid of the function limitations, please request a 30-day trial license for yourself.