Append a New Page for Digital Signature

This guide will explain the process of appending a new page with a signature to a PDF document.

Sample Input #

Before you begin #

You should get your API key from your UniCloud account.

If this is your first time using UniPDF SDK, follow this guide to set up a local development environment.

Project setup #

Clone the project repository #

In your terminal, clone examples repository using the following command: It contains the Go code we will be using for this guide.

git clone https://github.com/unidoc/unipdf-examples.git

Then navigate to the signatures folder in the unipdf-examples directory.

cd unipdf-examples/signatures

Configure environment variables #

Configure your license key using the following command: Replace the UNIDOC_LICENSE_API_KEY with your API credentials from your UniCloud account.

Linux/Mac #

export UNIDOC_LICENSE_API_KEY=PUT_YOUR_API_KEY_HERE

Windows #

set UNIDOC_LICENSE_API_KEY=PUT_YOUR_API_KEY_HERE

How it works #

The import section in lines imports UniPDF packages and other necessary libraries. The init function gets the API key and sets it to the license license.SetMeteredKey(os.Getenv(`UNIDOC_LICENSE_API_KEY`)).

The main function is defined in lines 37-81. In lines 38-44, of the main function, the input path and output paths are parsed from the command line arguments. Then a new PdfReader is instantiated from the input file in lines 47-53. Using addPage(pdfReader), a new page is added to the document. Then a signature is added to the new document using addSignature(pdfReader, totalPage, outputPath) in line 75.

The addPage function is defined in lines 83-99. This function adds a new page to the document using a model.PdfWriter object. Then the new document is returned in a buffer.

The addSignature function adds a signature to a document. The generateSigKeys() function generates and returns a private/public key pair, which is then used in the previous function to sign the document.

Run the code #

Run the code using the following command:

go run pdf_sign_new_page.go <INPUT_PDF_PATH> <OUTPUT_PDF_PATH>

Sample output #

Page 1 #

Page 2 #