pdf-form-fill

Simple PDF form fill, using [PDFtk]. Uses field data in xfdf format to help guarantee UTF-8 support.

All operations are non-blocking. Written in a rather ES6-ish style; use on Node 5.x and earlier will require transpiling.

Release as open source under the [ISC license].

$3

1. Make sure pdftk is available in your environment, preferably at least version 2.02.
2. npm install pdf-form-fill

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The API is minimal:
- fields(pdf) will return a [Promise] resolving with a simple object describing the PDF's available fields.
- fill(pdf, fields[, options]) will return a promise resolving with a [Readable sream] of the output PDF. the
following options are supported:
- flatten: Flatten the resulting PDF (default true)
- info: Info fields to be set in the output, such as CreationTime, ModTime, Title, Author, etc. Time
values should be Date objects; all others should be strings.
- verbose: Print stuff to the console (default false)

On error, the promises returned by both functions will reject with an Error object. For more details, read the
source code.

Setting any info values will require spawning a second pdftk instance and writing an intermediate PDF to a temporary
file (piping pdf output to pdftk turns out to be rather flaky). This will slow down the processing a bit; use
options.verbose to test the execution time on your systems.

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``js
const fs = require('fs')
const { fields, fill } = require('pdf-form-fill')

const srcPdf = '...'
const tgtPdf = '...'
const fields = { name1: 'Value 1', checkbox2: 'Yes' }

fields(srcPdf)
.then(shape => console.log(shape))
.catch(err => console.error(err))

const output = fs.createWriteStream(tgtPdf)
fill(scrPdf, fields)
.then(stream => stream.pipe(output))
.catch(err => console.error(err))
`

For a more complete example, see the [pdf-form-fill-server] source code.

$3

This tool is the product of frustration and incredulity, as none of the other PDF form-filling tools appeared to
work for my particular use case, requiring UTF-8 support in a macOS environment. For some reason, that works with
xfdf form data, but not with fdf. But then, of course, PDFtk isn't able to read that from stdin (unlike fdf`,
of course), so it needs to be written to a temporary file for it.

Some aspects of this code were inspired by [pdffiller-stream], but all the code was written from scratch for this.

[ISC license]: https://en.wikipedia.org/wiki/ISC_license
[pdf-form-fill-server]: https://github.com/eemeli/pdf-form-fill-server
[pdffiller-stream]: https://www.npmjs.com/package/pdffiller-stream
[PDFtk]: https://www.pdflabs.com/tools/pdftk-the-pdf-toolkit/
[Promise]: https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Promise
[Readable sream]: https://nodejs.org/api/stream.html#stream_class_stream_readable