Lua Requires Chilkat v11.7.0+

Find Out Whether a PDF Needs a Password Before Loading It

See more PDF Protection Examples

Demonstrates PreLoadCheck, which examines a PDF file without loading it and without any password. It reports whether the file is encrypted, by which method and algorithm, whether a password is needed to open it, and what its permissions are. An application uses it to decide whether to ask for a password, or which certificate it needs, before calling LoadFile. PreLoadCheckBd does the same for a PDF held in memory. 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 two_page_memo.pdf

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

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

local pdf = chilkat.Pdf.new()
local info = chilkat.JsonObject.new()

-- A PDF that is not encrypted.  Nothing but "encrypted" is reported for it.
local success = pdf:pre_load_check("qa_data/pdf/two_page_memo.pdf", info)
if not success then
    print(pdf.last_error_text)
    return
end

print("two_page_memo.pdf")
print("  encrypted: " .. tostring(info:bool_of("encrypted")))

-- A PDF that needs a password to open.
success = pdf:pre_load_check("qa_data/pdf/encrypted_user_password.pdf", info)
if not success then
    print(pdf.last_error_text)
    return
end

print("encrypted_user_password.pdf")
print("  encrypted: " .. tostring(info:bool_of("encrypted")))
print("  method: " .. info:string_of("method"))
print("  algorithm: " .. info:string_of("algorithm"))
print("  openPasswordRequired: " .. tostring(info:bool_of("openPasswordRequired")))

-- A PDF that opens without a password but is restricted.  The permissions are readable without
-- any password.
success = pdf:pre_load_check("qa_data/pdf/no_copy_permission.pdf", info)
if not success then
    print(pdf.last_error_text)
    return
end

print("no_copy_permission.pdf")
print("  encrypted: " .. tostring(info:bool_of("encrypted")))
print("  openPasswordRequired: " .. tostring(info:bool_of("openPasswordRequired")))
print("  may copy: " .. tostring(info:bool_of("permissions.copy")))

-- The typical use: ask for a password only when one is needed, then load.
success = pdf:pre_load_check("qa_data/pdf/encrypted_user_password.pdf", info)
if not success then
    print(pdf.last_error_text)
    return
end

if info:bool_of("openPasswordRequired") then
    -- An application would prompt for the password here.
    pdf.user_password = "secret"
end

success = pdf:load_file("qa_data/pdf/encrypted_user_password.pdf")
if not success then
    print(pdf.last_error_text)
    return
end

print("loaded, pages: " .. pdf.num_pages)

-- Sample output:

-- two_page_memo.pdf
--   encrypted: False
-- encrypted_user_password.pdf
--   encrypted: True
--   method: password
--   algorithm: rc4-128
--   openPasswordRequired: True
-- no_copy_permission.pdf
--   encrypted: True
--   openPasswordRequired: False
--   may copy: False
-- loaded, pages: 1