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Lua Requires Chilkat v9.5.0.90+

PDF Sign Unsigned Signature Field

See more PDF Signatures Examples

Demonstrates how to sign a PDF's unsigned signature field.

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Lua 
local chilkat = require("chilkat")

-- This example requires the Chilkat API to have been previously unlocked.
-- See Global Unlock Sample for sample code.

local pdf = chilkat.Pdf.new()

-- Load a PDF containing an unsigned signature field.
local success = pdf:load_file("qa_data/pdf/unsigned_sig_field/due_diligence.pdf")
if not success then
    print(pdf.last_error_text)
    return
end

-- A PDF with an unsigned signature field appears in Adobe Acrobat as shown below.
-- (When the mouse pointer is hovered over the field, a tooltip will likely show a message
-- such as "Unsigned signature field (Click to sign)".
-- This example code will automatically find the unsigned signature field,
-- and signs using your certificate.  It automatically sizes the text to the space alotted
-- for the signature.
-- image

-- Options for signing are specified in JSON.
local json = chilkat.JsonObject.new()

-- In most cases, the signingCertificateV2 and signingTime attributes are required.
json:update_int("signingCertificateV2", 1)
json:update_int("signingTime", 1)

-- We don't specify the page or a specific location because Chilkat will automatically
-- find the unsigned signature field and use its location and size and will scale the
-- signatures visual appearance (text + graphics) to the correct size required to fit.
-- We only need to indicate the desire to fill the unsigned signature field.
json:update_bool("appearance.fillUnsignedSignatureField", true)

-- If a PDF contains multiple unsigned signature fields,
-- the field to be signed can be chosen by name:
-- To list unsigned signature fields, see this example: List PDF Unsigned Signature Fields
json:update_string("unsignedSignatureField", "doctor_signature")

-- Note: If the PDF document contains multiple unsigned signature fields, Chilkat will
-- sign the 1st one found.

-- In this example, the appearance of the digital signature will contain three lines:
-- 1) The signing certificate's common name
-- 2) The current date/time
-- 3) Some arbitrary text.
-- The keyword "cert_cn" is replaced with the Certificate's Subject Common Name.
-- The keyword "current_dt" is replaced with the current date/time.
-- Any number of appearance text lines can be added.
json:update_string("appearance.text[0]", "Digitally signed by: cert_cn")
json:update_string("appearance.text[1]", "current_dt")
json:update_string("appearance.text[2]", "The crazy brown fox jumps over the lazy dog.")

-- This signature will include one of the built-in SVG graphics (green-check-grey-circle).
json:update_string("appearance.image", "green-check-grey-circle")
json:update_string("appearance.imagePlacement", "left")

-- Load the signing certificate. (Use your own certificate.)
local cert = chilkat.Cert.new()
success = cert:load_pfx_file("qa_data/pfx/myPdfSigningCert.pfx", "secret")
if not success then
    print(cert.last_error_text)
    return
end

-- Tell the pdf object to use the certificate for signing.
success = pdf:set_signing_cert(cert)
if not success then
    print(pdf.last_error_text)
    return
end

success = pdf:sign_pdf(json, "qa_output/due_diligence_signed.pdf")
if not success then
    print(pdf.last_error_text)
    return
end

print("The PDF has been successfully cryptographically signed.")

-- The appearance of the signature appears in Adobe Acrobat as shown below.
-- image