sign-pdf-lib

Signs pdf files. Uses pdf-lib to add signature to pdf files and node-forge to sign documents and verify the integrity of signed documents.

Installation

npm i sign-pdf-lib

Usage

Preparation

Instantiate signer:

const settings: SignatureSettings {
    signatureLength: ...,
    rangePlaceHolder: ...,

    signatureComputer: {
        certificate: await fse.readFile(...),
        password: '...'
    }
}
const pdfSigner = new PdfSigner(settings);

or

const settings: SignatureSettings {
    signatureLength: ...,
    rangePlaceHolder: ...,

    psignatureComputer: {
        emCertificate: await fse.readFile(..., 'ascii'),
        pemKey: await fse.readFile(..., 'ascii'),
        certificatePassword: '...'
    }
}
const pdfSigner = new PdfSigner(settings);

Digital signature parameters preparation:

const parameters: SignDigitalParameters = {
    pageNumber: 1,

    signature: {
        name: 'Test Signer',
        location: 'Timisoara',
        reason: 'Signing',
        contactInfo: '[email protected]'
    },

    visual: {
        rectangle: { 
            left: 50, 
            top: 641, 
            right: 264, 
            bottom: 711
        },
        background: await fse.readFile(...),
        texts: [{
            lines: [ 
                'JOHN', 
                'DOE'
            ]}, {
            lines: [ 
                'Digitally signed by', 
                'JOHN DOE', 
                'Date: 2023.11.03', 
                '20:28:46 +02\'00\''
            ]}
        ]
    }
};

IMPORTANT: if coordinates are negative, they are considered from right or bottom.

For non visual signatures, just omit visual field:

const parameters: SignDigitalParameters = {
    pageNumber: 1,

    signature: {
        name: 'Test Signer',
        location: 'Timisoara',
        reason: 'Signing',
        contactInfo: '[email protected]'
    }
};

If you want a specific name for signature, specify it:

const parameters: SignDigitalParameters = {
    pageNumber: 1,
    name: 'Signature2',
    ...
};

Sign PDF

const pdf = await fse.readFile(...); 
const signedPdf = await pdfSigner.signAsync(pdf, parameters);

Add signature placeholder

const pdf = await fse.readFile(...); 
const placeholderPdf = await pdfSigner.addPlaceholderAsync(pdf, parameters);

Digital signature field parameters preparation:

const parameters: AddFieldParameters = {
    pageNumber: 1,

    rectangle: { 
        left: 50, 
        top: 641, 
        right: 264, 
        bottom: 711
    }
};

IMPORTANT: if coordinate are negative, they are considered from right or bottom.

If you want a specific name for signature, specify it:

const parameters: AddFieldParameters = {
    pageNumber: 1,
    name: 'Signature2',
    ...
};

Add signature field

const pdf = await fse.readFile(...); 
const fieldPdf = await pdfSigner.addFieldAsync(pdf, parameters);

Get signature field list

const pdf = await fse.readFile(...); 
const fields = await pdfSigner.getFieldsAsync(pdf);

Field signature parameters preparation:

const parameters: SignFieldParameters = {
    fieldName: 'Signature1,

    signature: {
        name: 'Test Signer',
        location: 'Timisoara',
        reason: 'Signing',
        contactInfo: '[email protected]'
    },

    visual: {
        background: await fse.readFile(...),
        texts: [{
            lines: [ 
                'JOHN', 
                'DOE'
            ]}, {
            lines: [ 
                'Digitally signed by', 
                'JOHN DOE', 
                'Date: 2023.11.03', 
                '20:28:46 +02\'00\''
            ]}
        ]
    ]
};

Sign field

const pdf = await fse.readFile(...); 
const signedPdf = await pdfSigner.signFieldAsync(pdf, parameters);

Verify signatures

const pdf = await fse.readFile(...); 
const checks = await pdfSigner.verifySignaturesAsync(pdf);

IMPORTANT!: This function checks only the integrity of signatures (if the document has been changed after it has been signed).

Visual signature parameters preparation:

const parameters: SignVisualParameters = {
    pageNumber: 1,
    rectangle: { 
        left: 50, 
        top: 641, 
        right: 264, 
        bottom: 711
    },

    background: await fse.readFile(...),
    texts: [{
        lines: [ 
            'JOHN', 
            'DOE'
        ]}, {
        lines: [ 
            'Digitally signed by', 
            'JOHN DOE', 
            'Date: 2023.11.03', 
            '20:28:46 +02\'00\''
        ]}
    ]
};

IMPORTANT: if coordinates are negative, they are considered from right or bottom.

If the signature is placed relatively to the bottom pf the page use reverseY to fix the problem:

const parameters: SignVisualParameters = {
    ...
    reverseY: true,
    ...
};

Visual sign PDF

const pdf = await fse.readFile(...); 
const signedPdf = await pdfSigner.signVisualAsync(pdf, parameters);