Common Pdf

CommonPdf wraps a small subset of pdftk aiming to provide performant pdf operations in node.js applications. Though not necessary CommonPdf assumes execution in AWS Lambda. Instructions for setup are described below.

API

• concat
• fillform
• rotate
• stamp

Getting Started

• Install pdftk and put on your path
• Install CommonPdf npm i -S commonpdf
• Test pdftk & CommonPdf installation npm test
• Import only what you need

const Rotate = require( 'commonpdf' ).Rotate,
    Concat = require( 'commonpdf' ).Concat,
    FillForm = require( 'commonpdf' ).FillForm,
    Stamp = require( 'commonpdf' ).Stamp

Basic Usage

All classes expose a write() method, and every write returns a promise. The resolved promise will contain the file path to the newly written file.

File names can either be passed in as an optional parameter or if undefined a unique name will be generated. This is done to avoid name conflicts in AWS Lambda (files written to /tmp may persist across multiple function invocations).

Documentation is currently vague and incomplete. Until this has been remedied (better docs is my current milestone) exploring the .spec.js files in the /src directory will provide working examples that you may follow.

Concat:

Concat accepts an array of pdf file paths. Concat can also be used to split a document. Given a single Pdf input define optional parameter Array<{start:number, end:number|string}>

const Concat = require( 'commonpdf' ).Concat,
    pdfs = ['fileA.pdf', 'fileB.pdf'],
    opts = '/outfile.pdf' 
new Concat(pdfs, opts /*optional*/)
    .write()
    .then(outfilePath => {
    	// do something 
    })

FillForm:

FillForm requires FdfGenerator, this class will be briefly covered here, for more info look at fdf-generator.spec

const FillForm = require('commonpdf').FillForm,
    FdfGenerator = require('commonpdf').FDFGenerator,
    fdfParameters = [
    	{fieldname:'hierarchical field name', fieldvalue:'a string value'},
    	{fieldname:'abutton', fieldvalue:true/false}
    ],
    pdfFilePath = '/path/to/target.pdf'

const fdf = new FdfGenerator(pdfFilePath, fdfParameters)

fdf.write()
    .then(fdfFile => {
    	return new FillForm(fdfFile, pdfFilePath).write()
    })
    .then(outFilePath => {
    	// do something will filled pdf form
    })

Stamp:

const Stamp = require('commonpdf').Stamp,
    img = 'data:image/png;base64,.....',
    pdf = 'path/to/pdf',
    pageNumber = 1,
    dimensions = {width:100, height:100, x:100, y:100}
 
new Stamp(pdf).write(img, pageNumber, dimensions)    
    .then(outfile => {
    	// do something with newly stamped pdf 
    })

Rotate:

const Rotate = require('commonpdf').Rotate,
    pdf = 'pdf/file/path',
    pageNumber = 2,
    config = {direction:'east'}
    
new Rotate(pdf, pageNumber, config)
    .write()
    .then(outfile => {
    	// do something
    })

Todo

• pdf view portal (web component) Moved to separate repo (CommonPdfComponent)
• code documentation Added typescript definition file
• contributor details
• expand tested pdf's Added test-data directory for unit testing
• add complete list of command line parameter options
• add options documentation
• improve README
• file name parameter standardization (on the constructor or on the write())
• better error handling, human readable error messages

Run as Lambda

Create a zip with

./dist.sh

Then, simply upload this ZIP to AWS Lambda

How it Works

AWS Lambda supports binary dependencies by allowing them to be included in uploaded ZIP files. However, because Amazon Linux does not support PDFtk or GCJ, PDFtk was built from source in CentOS, a close relative of Amazon Linux. I spun up a CentOS 6 machine in EC2 and followed the instructions on the PDFtk website to build PDFtk from source.

sudo yum install gcc gcc-java libgcj libgcj-devel gcc-c++

wget https://www.pdflabs.com/tools/pdftk-the-pdf-toolkit/pdftk-2.02-src.zip

unzip pdftk-2.02-src.zip

cd pdftk-2.02-dist/pdftk

make -f Makefile.Redhat

sudo make -f Makefile.Redhat install

Then I copied the resulting pdftk binary and /usr/lib64/libgcj.so.10 shared library into the bin/ directory of my Lambda project.

The entry point to the lambda function, index.js, alters the PATH and LD_LIBRARY_PATH environment variables to let the system know where to find the binary and the GCJ dependency.

Using PDFtk in Amazon Linux

It should be possible to use the PDFtk binary and GCJ shared library located in the bin/ directory of this file to run PDFtk in Amazon Linux on EC2. Simply copy them onto the machine and put them in the correct path, or call them directly:

LD_LIBRARY_PATH=/path/to/libgcj.so.10 /path/to/pdftk --version

let exec = require('child_process').exec;

// Set the PATH and LD_LIBRARY_PATH environment variables.
process.env['PATH'] = process.env['PATH'] + ':' + process.env['LAMBDA_TASK_ROOT'] + '/bin';
process.env['LD_LIBRARY_PATH'] = process.env['LAMBDA_TASK_ROOT'] + '/bin';

exports.handler = function handler (event, context) {
	exec('pdftk --version', context.done);
};