Absolutely possible! You don’t have to rely on HTML-to-PDF tools like Prawn or Wicked PDF to populate existing fillable PDFs—there are dedicated Ruby libraries that let you directly map your database/form data to PDF form fields. Here are two reliable approaches I’ve used in production:

Option 1: pdf-forms (Based on PDFtk) #

This gem wraps PDFtk, a popular command-line tool for manipulating PDFs. It’s straightforward and works great if you can install PDFtk on your system.

Step 1: Set Up Dependencies #

First, install PDFtk:

• On Ubuntu/Debian: sudo apt-get install pdftk-java
• On macOS: brew install pdftk-java
• On Windows: Grab the official installer (I haven’t tested this personally, but it’s widely supported)

Then install the gem:

gem install pdf-forms

Step 2: Fill the Form with Data #

Here’s a quick example using data from your database or form submission:

require 'pdf_forms'

# Initialize the PDFtk wrapper (adjust the path to pdftk if your system uses a different location)
pdftk = PdfForms.new('/usr/bin/pdftk')

# Paths to your fillable template and the output filled PDF
template_path = './templates/client_intake_form.pdf'
output_path = './filled_forms/client_jane_smith.pdf'

# Data hash—keys MUST match the exact field names in your PDF template
form_data = {
  'client_full_name' => 'Jane Smith',
  'client_email' => 'jane.smith@example.com',
  'client_phone' => '555-7890',
  'service_requested' => 'Web Development',
  'project_budget' => '$15,000'
}

# Fill the form and save the result
pdftk.fill_form(template_path, output_path, form_data)

Pro Tip: Get Exact PDF Field Names #

To avoid mismatches between your data keys and the PDF’s field names, run this command to list all fields in your template:

pdftk ./templates/client_intake_form.pdf dump_data_fields

Or fetch fields programmatically with the gem:

fields = pdftk.get_fields(template_path)
fields.each { |field| puts "Field name: #{field[:name]}" }

Option 2: hexapdf (Pure Ruby, No External Dependencies) #

If you run into issues installing PDFtk (like on newer macOS versions), HexaPDF is a pure-Ruby PDF processing library that handles form filling without external tools. It’s a great alternative for cross-platform projects.

Step 1: Install the Gem #

gem install hexapdf

Step 2: Fill the Form #

Here’s how to implement it:

require 'hexapdf'

template_path = './templates/client_intake_form.pdf'
output_path = './filled_forms/client_jane_smith.pdf'

form_data = {
  'client_full_name' => 'Jane Smith',
  'client_email' => 'jane.smith@example.com',
  'service_requested' => 'Web Development'
}

HexaPDF::Document.open(template_path) do |doc|
  acro_form = doc.acro_form
  form_data.each do |field_name, value|
    # Locate the field by name and set its value
    field = acro_form.field(field_name)
    next unless field # Skip if the field doesn't exist in the template
    
    field.value = value
    # Optional: Mark fields as read-only to prevent post-filling edits
    field.read_only = true
  end
  # Save the completed PDF
  doc.write(output_path)
end

Key Notes #

• Make sure your PDF template is fillable (not flattened). If you only have a static PDF, convert it to a fillable form first using tools like Adobe Acrobat or LibreOffice.
• For checkboxes or radio buttons, the required value might be specific (e.g., 'Yes' for a checked box). Test with your template to find the correct trigger values.
• If you want to flatten the filled PDF (so users can’t edit it later), use pdftk.fill_form(..., flatten: true) with pdf-forms, or add doc.acro_form.flatten before writing the file with HexaPDF.

内容的提问来源于stack exchange，提问作者RIzu