Lua Requires Chilkat v11.7.0+

Fill a PDF Template: Replace {{placeholders}} with Values

See more PDF Text Replacement Examples

Demonstrates the TextReplace method on an invoice template whose values are written as placeholders such as {{customer}} and {{total}}. The "placeholders" object names each placeholder and the text to put in; every occurrence on the page is replaced, including a placeholder inside a sentence or inside a label such as "Tax ({{taxRate}}):". The text is redrawn with the font the template used, so the result looks like the template, and a value that is right-aligned in the template stays right-aligned. The changes are written by WriteFile. Lua

local chilkat = require("chilkat")

-- This example requires the Chilkat API to have been previously unlocked.
-- See Global Unlock Sample for sample code.

-- The PDF used in this example is available at invoice_template.pdf

local pdf = chilkat.Pdf.new()
local success = pdf:load_file("qa_data/pdf/invoice_template.pdf")
if not success then
    print(pdf.last_error_text)
    return
end

-- The template has these placeholders in its page text:
--   {{customer}} (twice: "Bill To:" and the closing sentence), {{date}}, {{po}},
--   two item rows: {{qty1}} {{desc1}} {{price1}} {{amount1}} and {{qty2}} {{desc2}} {{price2}} {{amount2}},
--   {{subtotal}}, "Tax ({{taxRate}}):" with {{tax}}, and {{total}}.
local json = chilkat.JsonObject.new()
json:update_string("placeholders.customer", "Acme Corp")
json:update_string("placeholders.date", "2026-10-18")
json:update_string("placeholders.po", "PO-88213")
json:update_string("placeholders.qty1", "2")
json:update_string("placeholders.desc1", "Cordless drill, 18 V")
json:update_string("placeholders.price1", "$460.00")
json:update_string("placeholders.amount1", "$920.00")
json:update_string("placeholders.qty2", "6")
json:update_string("placeholders.desc2", "Galvanized hinge, 4 inch")
json:update_string("placeholders.price2", "$12.50")
json:update_string("placeholders.amount2", "$75.00")
json:update_string("placeholders.subtotal", "$995.00")
json:update_string("placeholders.taxRate", "7.35%")
json:update_string("placeholders.tax", "$73.13")
json:update_string("placeholders.total", "$1,068.13")

-- "apply" makes every replacement, or none: if any value cannot be drawn with the
-- template's font, the method returns false, the PDF is unchanged, and jsonOut says why.
local jsonOut = chilkat.JsonObject.new()
success = pdf:text_replace("apply", json, jsonOut)
if not success then
    print("Not applied: " .. jsonOut:emit())
    if not success then
        print(pdf.last_error_text)
        return
    end
end

-- One entry per placeholder: the pages it was found on and how many times it was replaced.
local i = 0
local count_i = jsonOut:size_of_array("replacements")
while i < count_i do
    jsonOut.i = i
    print(jsonOut:string_of("replacements[i].field") .. ": " .. jsonOut:int_of("replacements[i].count") .. " on page(s) " .. jsonOut:string_of("replacements[i].pages"))
    i = i + 1
end

-- The replacements stay in memory until the PDF is written.
success = pdf:write_file("qa_output/invoice_filled.pdf")
if not success then
    print(pdf.last_error_text)
    return
end

print("Wrote qa_output/invoice_filled.pdf")

-- Sample output:

-- customer: 2 on page(s) 1
-- date: 1 on page(s) 1
-- po: 1 on page(s) 1
-- qty1: 1 on page(s) 1
-- desc1: 1 on page(s) 1
-- price1: 1 on page(s) 1
-- amount1: 1 on page(s) 1
-- qty2: 1 on page(s) 1
-- desc2: 1 on page(s) 1
-- price2: 1 on page(s) 1
-- amount2: 1 on page(s) 1
-- subtotal: 1 on page(s) 1
-- taxRate: 1 on page(s) 1
-- tax: 1 on page(s) 1
-- total: 1 on page(s) 1
-- Wrote qa_output/invoice_filled.pdf