Watermarking a PDF document with a QR code

In this example we will follow a two-step process to first create (and store) an image of a QR code and then use that image to watermark a PDF document.

This example demonstrates several features of the Document Alchemy API:

1. How to create a QR code image.

2. How to create a document directly within the Document Alchemy file-store.

3. How to use a stored document within another API call.

4. How to watermark a PDF document (using a stored image and an uploaded PDF file).

5. How to delete a file from the Document Alchemy file-store.

Installing

(These instructions assume you've already installed a modern version of Node.js/IO.js. If you haven't yet, see https://nodejs.org/ for details.)

To simplify the task, this example uses the popular request module (on GitHub at request/request).

To install the module, simply run:

1npm install

from within this directory (the one containing package.json and this README file). This will download and install all of the necessary third-party libraries.

Running

To run this example, you will need:

1. A DocumentAlchemy API key. If you don't have one yet, you can obtain one immediately by signing up for DocumentAlchemy.

2. A PDF document to watermark.

The general format for running this program is this:

1node qr-watermark.js <API-KEY> <TEXT-TO-ENCODE> <PDF-TO-WATERMARK> [<OUTPUT-FILE-NAME>]

For example, if your API key value is HbblCNv7gLN2pasWFK44, the command:

1node qr-watermark.js HbblCNv7gLN2pasWFK44 "http://www.example.com/" myDocument.pdf watermarkedDocument.pdf

will create (or overwrite) the file watermarkedDocument.pdf, containing a copy of myDocument.pdf with a QR code (pointing to www.example.com) stamped on every page.

The output of the program may look something like this:

Creating the QR code...
...Success! Created and stored QR code as document ID "8cxwka1gbjoflxrqi2ux2z2".
Watermarking the PDF document using that stored image...
...Success! Watermarked PDF document saved at "watermarkedDocument.pdf".
Deleting the QR code...
...Success! Stored document deleted from the server.

(Note that qr-watermark.js is also directly executable via:

1qr-watermark.js <API-KEY> <TEXT-TO-ENCODE> <PDF-TO-WATERMARK> [<OUTPUT-FILE-NAME>]

if your shell recognizes the #!/usr/bin/env node hash-bang identifier.)

How it works

Please review the code and comments found in qr-watermark.js for a detailed explanation of the process.