Pdf-lib: How to fill form checkbox fields

[pammann-work]

Can pdf-lib be used to programmatically fill out checkbox fields in a template PDF?
Analog to #48

[Hopding]

Update (9/16/2020)

pdf-lib now has form creation and filling APIs that should be used instead of the below example(s). See the form filling JSFiddle for a working example. Additional information is available in the README and API docs. The PDFCheckBox.check method is of particular relevance to this issue.

Original

Hello @pammann-work!

I created an example script demonstrating how to do this: pdf-lib_check_box_form_fill_example.zip

You can run the script with the following commands (you may have to tweak them a bit if you're running Windows):

unzip pdf-lib_check_box_form_fill_example.zip
cd pdf-lib_check_box_form_fill_example
npm install
node index.js

Here's the input PDF: simple_form.pdf
And here's the output: filled_form.pdf

Here's a snippet from the script showing the gist of the process:

const getAcroFields = pdfDoc => {
  if (!pdfDoc.catalog.getMaybe('AcroForm')) return [];
  const acroForm = pdfDoc.index.lookup(pdfDoc.catalog.get('AcroForm'));

  if (!acroForm.getMaybe('Fields')) return [];
  const acroFields = pdfDoc.index.lookup(acroForm.get('Fields'));

  return acroFields.array.map(pdfDoc.index.lookup);
};

const findAcroFieldByName = (pdfDoc, name) => {
  const acroFields = getAcroFields(pdfDoc);
  return acroFields.find(acroField => {
    const fieldName = acroField.getMaybe('T');
    return !!fieldName && fieldName.string === name;
  });
};

const pdfDoc = PDFDocumentFactory.load(fs.readFileSync('./simple_form.pdf'));

const fooCheckBox = findAcroFieldByName(pdfDoc, 'FooCheckBox');
const barCheckBox = findAcroFieldByName(pdfDoc, 'BarCheckBox');
const quxCheckBox = findAcroFieldByName(pdfDoc, 'QuxCheckBox');
const bazCheckBox = findAcroFieldByName(pdfDoc, 'BazCheckBox');

console.log('Selecting "Foo" and "Qux" boxes...');
fooCheckBox.set('V', PDFName.from('Yes'));
quxCheckBox.set('V', PDFName.from('Yes'));

console.log('Saving modified PDF...');
const pdfBytes = PDFDocumentWriter.saveToBytes(pdfDoc);
fs.writeFileSync('./filled_form.pdf', pdfBytes);

console.log('Filled-in Form Written To ./filled_form.pdf');

I hope this helps! Please let me know if you have any additional questions.

[pammann-work]

@Hopding Thank you very much for this example, this helped a lot.

When i look at your filled_form.pdf, i do not see the checkbox checked (in Acrobat Reader + Firefox). I fiddled a bit around and found out that i need to set 'AS' as well:

this works:

fooCheckBox.set('V', PDFName.from('Yes'));
fooCheckBox.set('AS', PDFName.from('Yes'));

PS: I am using v0.6.2 of pdf-lib

[astanet]

I updated the example on https://github.com/Hopding/pdf-lib/issues/109#issuecomment-493761539 to v.1.1.1. to learn this library.
pdf-lib_check_box_form_fill_example2.zip
Please correct if I am missing something.
Thanks.

[zepekenio]

Hi, i can check my checkboxs with
field.set(PDFName.of('V'), PDFName.of('Yes'))
field.set(PDFName.of('AS'), PDFName.of('Yes'));
When i open the pdf locally, the checkbox are checked.
But when im sending the pdf by mail or other, i cant see the checkbox checked.

Do you have the same issue ?
Im using v1.1.1

[Hopding]

@astanet thank you for updating the example!

[Hopding]

@zepekenio It looks like I omitted a step in my original example. It's also necessary to set the NeedAppearances field on the AcroForm (like I did here). Here's an updated version of the example for version 1.3.0 that correctly sets the NeedAppearances field:

pdf-lib_check_box_form_fill_example3.zip

And here's the gist of the script:

const fs = require('fs');
const { PDFDocument, PDFName, PDFBool, PDFArray } = require('pdf-lib');

const getAcroForm = pdfDoc => {
  return pdfDoc.catalog.lookup(PDFName.of('AcroForm'));
};

const getAcroFields = pdfDoc => {
  const acroForm = getAcroForm(pdfDoc);
  if (!acroForm) return [];

  const fieldRefs = acroForm.lookupMaybe(PDFName.of('Fields'), PDFArray);
  if (!fieldRefs) return [];

  const fields = new Array(fieldRefs.size());
  for (let idx = 0, len = fieldRefs.size(); idx < len; idx++) {
    fields[idx] = fieldRefs.lookup(idx);
  }
  return fields;
};

const findAcroFieldByName = (pdfDoc, name) => {
  const acroFields = getAcroFields(pdfDoc);
  return acroFields.find(acroField => {
    const fieldName = acroField.get(PDFName.of('T'));
    return !!fieldName && fieldName.value === name;
  });
};

const pdfDoc = await PDFDocument.load(fs.readFileSync('./simple_form.pdf'));

const acroForm = getAcroForm(pdfDoc);
acroForm.set(PDFName.of('NeedAppearances'), PDFBool.True);

const fooCheckBox = findAcroFieldByName(pdfDoc, 'FooCheckBox');
const quxCheckBox = findAcroFieldByName(pdfDoc, 'QuxCheckBox');

console.log('Selecting "Foo" and "Qux" boxes...');
fooCheckBox.set(PDFName.of('V'), PDFName.of('Yes'));
fooCheckBox.set(PDFName.of('AS'), PDFName.of('Yes'));
quxCheckBox.set(PDFName.of('V'), PDFName.of('Yes'));
quxCheckBox.set(PDFName.of('AS'), PDFName.of('Yes'));

console.log('Saving modified PDF...');
const pdfBytes = await pdfDoc.save();
fs.writeFileSync('./filled_form.pdf', pdfBytes);

[coler-j]

@Hopding I am following the instructions above and my code looks like this:

myCheckBox.set(PDFName.of('V'), PDFName.of('Yes'));
myCheckBox.set(PDFName.of('AS'), PDFName.of('Yes'));

I am also doing acroForm.set(PDFName.of('NeedAppearances'), PDFBool.True);

However, my saved check box is not checked:

Setting text field works fine, it is only setting of checkboxes which doesn't seem to work.

Are the instructions above no longer accurate?

[coler-j]

We just ended getting the Rectangle dimensions of the field and putting a text 'x' over the selected checkbox.

[Hopding]

pdf-lib now has form creation and filling APIs that should be used instead of the above example(s). See the form filling JSFiddle for a working example. Additional information is available in the README and API docs. The PDFCheckBox.check method is of particular relevance to this issue.