B4X

PDF Signature Page Location

See more PDF Signatures Examples

This example demonstrates how to specify the location of a PDF signature on a page.

Note: This example requires Chilkat v9.5.0.85 or greater.

B4X

Dim success As Boolean = False

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

Dim pdf As ChilkatPdf
pdf.Initialize("pdf")

'  Load a PDF to be signed.
'  The "hello.pdf" is available at https://chilkatsoft.com/hello.pdf
success = pdf.LoadFile("qa_data/pdf/hello.pdf")
If success = False Then
    Log(pdf.LastErrorText)
    Return
End If


'  Options for signing are specified in JSON.
Dim json As ChilkatJsonObject
json.Initialize

'  In most cases, the signingCertificateV2 and signingTime attributes are required.
json.UpdateInt("signingCertificateV2", 1)
json.UpdateInt("signingTime", 1)

'  When cryptographically signing a PDF, the signature's appearance can be placed on a specific
'  page in the PDF document, and at a specified location on the page.
'  The 1st page of the PDF document is page number 1 (we don't use 0-based numbering for PDF page numbers).
'  The PDF object has a NumPages property, so we can use it to sign on the last page of the PDF.
json.UpdateInt("page", pdf.NumPages)

'  appearance.y and appearance.x JSON properties control the x,y location of the signature.
'  The "appearance.y" can be "top" or "bottom".
'  The "appearance.x" can be "left", "middle", or "right".
'  It is also possible to specify exact PDF location in user space coordinates, which is discussed below.
json.UpdateString("appearance.y", "bottom")
json.UpdateString("appearance.x", "middle")

'  In this example, the fontScale (in combination with the number of appearance text lines and the length of the longest text line),
'  automatically determine the width/height of the signature text box. Any included graphic (JPG image or built-in SVG) is automatically
'  scaled to fit. It is alternatively possible to specify the desired width/height of the signature rectangle.  In that case
'  you would NOT specify a fontScale because Chilkat would automatically chose a font scale to fit the text to the desired rectangle.
'  This example demonstrates how to specify the exact width/height of the PDF signature text box.
json.UpdateString("appearance.fontScale", "9.0")

json.UpdateString("appearance.text[0]", "Digitally signed by: cert_cn")
json.UpdateString("appearance.text[1]", "current_dt")
json.UpdateString("appearance.image", "document-accepted")
json.UpdateString("appearance.imagePlacement", "left")
json.UpdateString("appearance.imageOpacity", "100")

'  Load the signing certificate. (Use your own certificate.)
Dim cert As ChilkatCert
cert.Initialize("cert")
success = cert.LoadPfxFile("qa_data/pfx/myPdfSigningCert.pfx", "pfx_password")
If success = False Then
    Log(cert.LastErrorText)
    Return
End If


'  Tell the pdf object to use the certificate for signing.
success = pdf.SetSigningCert(cert)
If success = False Then
    Log(pdf.LastErrorText)
    Return
End If


success = pdf.SignPdf(json, "qa_output/hello_signed.pdf")
If success = False Then
    Log(pdf.LastErrorText)
    Return
End If


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

'  The appearance of the signature appears in Adobe Acrobat as shown here:

'  ----------------------------------------------------------------------------------------------------
'  *** Scroll down for information about specifying the PDF signature x,y location in user space coordinates.
'  ----------------------------------------------------------------------------------------------------

'  (image:https://example-code.com/images/bottom_middle_signature.jpg/endImage)

'  The x,y coordinates of a PDF page are in "user space", called "points", and there are 72 pointes per inch.
'  A PDF page (8.5" x 11") is 612 points wide and 792 points high.
'  The bottom left is at 0,0.    The top right is at 612,792.
'  
'  To specify the location of a signature rectangle, the "appearance.y" is the y coordinate of the top of the signature rectangle,
'  and the "appearance.x" is the x coordinate of the left of the signature rectangle.
'  Therefore, to position the signature rectangle at the exact top/left of the page, we do this:

json.UpdateString("appearance.y", "792")
json.UpdateString("appearance.x", "0")

json.UpdateString("appearance.text[0]", "Digitally signed again by: cert_cn")
json.UpdateString("appearance.text[1]", "current_dt")
json.UpdateString("appearance.image", "document-accepted")
json.UpdateString("appearance.imagePlacement", "right")

Dim pdf2 As ChilkatPdf
pdf2.Initialize("pdf2")
success = pdf2.LoadFile("qa_output/hello_signed.pdf")
success = pdf2.SetSigningCert(cert)

success = pdf2.SignPdf(json, "qa_output/hello_signed2.pdf")
If success = False Then
    Log(pdf2.LastErrorText)
    Return
End If


Log("The PDF has been successfully cryptographically signed again.")

'  Here we have the PDF with the signature just added at the exact top/left.
'  (image:https://example-code.com/images/pdf_signature_top_left.jpg/endImage)