Secure PDF Forms

PDF Form Protection – lock form fields, stop editing, secure submission

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  PDF form security issues

PDF forms are an easy way to collect user data, but they suffer from multiple security issues:

  1. Form content (text and fields on the form) can be easily modified.
  2. Submitted field content can be altered after submission.  Adobe Acrobat and other PDF editing software enable users to save fillable forms after data has been entered and edit it later – there is nothing to stop third parties from removing or editing this data either.
  3. Digitally signed PDF files are not as secure as you might think.  Objects that are being or have been signed may contain references to elsewhere in the PDF document or to somewhere outside the document where the content has not been digitally signed, and that content can be altered.

  The Adobe Solution to PDF form protection

Adobe Acrobat (and other PDF editing software) enable users to flatten the PDF by using the ‘Print to PDF file’ option, which creates a graphic image of the document inside a PDF file.  This can help stop users from altering field data after submission (although someone could still edit the graphic image or use an OCR tool to make it editable again).  However, you may not want users to be able to print and copy the form, especially if you are selling a PDF form and want to stop it from being edited and resold by someone else.

Adobe also lets you apply restrictions to PDF forms (password protect PDF form) so that users can fill and sign a form but not change or edit it.  These restrictions are enforced using the standard Adobe PDF password protection (encrypt with password option) and can be easily removed – see removing PDF passwords.  So, Adobe PDF form security with passwords is completely useless.

  How to edit a secured PDF form

For an example of how easy it is to edit a secured PDF form that was protected by Adobe, follow along below:

  1. Go to the SmallPDF unlock PDF tool and upload a protected form.
  2. Tick “I pinky swear that I have the right to edit this form and remove its protection” and press “Unlock PDF!”
  3. Press the “Download” button and open the unprotected file in your PDF viewer/editor of choice to modify it.

That’s all a user needs to do if they want to unlock your PDF form.  They can now do whatever they like with it, including distributing it to unauthorized users or changing its content.

Stop PDF forms from being edited or form data modified after submission

  • Protect form content from copying and saving

    Locklizard’s DRM controls ensure users cannot copy your forms. It:

    • protects form content from being copied (users cannot copy and paste content to other applications)
    • stops screen grabbing tools (so users cannot take high-quality screenshots)
    • saves fillable PDF forms as read only
    • prevents PDF forms from being saved to unprotected formats
    • stops users sharing PDF forms– forms are locked to authorized users’ devices

    For additional PDF form security, you can lock PDF forms to country and IP locations.

  • Protect PDF form & form fields from editing

    Safeguard PDF Security enables you to lock a PDF form and its fields so that form content cannot be edited and modified.

    It automatically saves fillable PDFs as read only so that form content is always protected.

    Form fields cannot be modified – only data can be entered by a user.

    The Safeguard Secure PDF Viewer does not make any functionality available to users that enables them to edit form content.  Your form will therefore remain the way you intended it to be.

  • Control or stop printing

    Disabling printing (this is applied by default) is an important aspect of secure PDF form distribution, as it ensures printed copies cannot be made available to unauthorized users or forms scanned back in and altered.

    However, if you want users to be able to make printed copies then you can:

    • limit the number of high-quality prints allowed
    • enforce color documents to be printed in black & white or grayscale
    • log each time a form is printed (when and where this occurred)
    • watermark printed content with user-identifiable information (using dynamic watermarksthat insert user and system information at print time) to discourage photocopying and subsequent distribution

    Locklizard automatically prevents printing to file drivers so that users cannot print to unprotected PDF files and other digital document formats.

  • Control form expiry

    Setting a PDF form to expire can be useful if your form is part of teaching material or a competition (say a quiz) where you want to time limit access.

    Expiry-controlled forms stop being available automatically so you do not have to spend time administering them manually.

    Safeguard PDF security enables you to securely distribute forms that automatically expire:

    • on a fixed date
    • after a number of days use
    • after a number of views
    • after a number of prints

    So you have full control over how long your secure PDF forms can be viewed and printed.

  • Secure PDF form submission & form field encryption

    Secure PDF form submission is an important part of form security since it ensures data that has been entered by a user cannot be modified after submission.

    With a normal PDF form, form data is sent in plain text because it is part of the PDF document.  This means that it is not protected when stored on a server.

    Encrypting form fields (encoding form fields) ensures they cannot be modified after the form has been filled out and submitted.

    Some companies use JavaScript to encrypt form data, but even Adobe advises users not to enable JavaScript in PDF files due to PDF security issues – it is regularly used by hackers to gain access to computers.

    Locklizard stores PDF form data in an XML file which can be encrypted separately when the form is submitted.  This ensures sensitive data like credit card information is always protected.

  • Revoking access

    There are going to be times when you have distributed forms that are no longer valid or contracts with third parties are no longer active.

    Locklizard enables you to instantly revoke access to PDF forms for all or individual users, or revoke user access to all or individual forms in one go so that they are no longer accessible.

    Being able to revoke access is an important feature of secure PDF form distribution since it ensures you retain full control over users’ access to documents regardless of where they are located.

  • Logging form use

    There may be occasions when you want to see if a PDF form you have distributed securely has been viewed and/or printed, and where, when, and how often this occurred.

    Locklizard enables you to track PDF files so you can identify any suspicious activity and instantly revoke access if required.

How do I secure PDF fillable forms / lock PDF form after filling out using Safeguard PDF Security?

How to save fillable PDF as read only or PDF form as read only

To save a fillable PDF as read only (protect PDF form from editing and protect form content from being copied):

  1. In Windows File Explorer, right-click on the PDF file that contains the form (the PDF could consist of just a form or multiple document pages and a form) and select the ‘Make secure PDF‘ option.
  2. Select the DRM controls you want to apply (access, expiry, etc.).
  3. Press the ‘Publish’ button.

Safeguard PDF Security will automatically save the fillable PDF form as read only, lock the PDF form against editing and modification, and prevent the PDF form from being saved in unprotected formats.  Once a form is protected, users can only enter data in the form fields provided.

Safeguard PDF Security supports basic forms functionality.  Custom user JavaScript is NOT supported to prevent forms from being exposed to AcroForm vulnerabilities.

  Why lock a PDF form with Safeguard PDF Security?

Locking PDF forms and form fields with Safeguard is more secure than Adobe password protection & simple.

Safeguard automatically protects PDF forms from unauthorized sharing:

  • PDF forms are always locked from being changed (read only).
  • Users cannot copy or save protected PDF forms into unprotected files, edit or print them.
  • There are no passwords to enter or remove.
  • If a locked PDF form is sent to an unauthorized user they will not be able to open it since they need a decryption key.
  • PDF forms are automatically locked to authorized devices.
  • You can lock users to country and IP locations.
  • Stops Windows print screen and third party screen grabbers from grabbing screenshots.
  • Revoke protected PDF forms at any time.

Secure PDF form submission & distributing a PDF form securely

With password-based systems such as Adobe PDF password protection, users can share PDF forms and their passwords with others.  In other words, PDF password protection does not enable you to distribute a PDF form securely.

Locklizard uses public key technology with a secure and secret key transfer mechanism so that keys are never exposed to users and interfaces, where they can be readily exploited.  Document keys are locked to authorized devices within a keystore, so if the keystore is copied to another device it will fail to work.

Locklizard’s PDF security stops users from sharing protected PDF forms with others and enables you to securely distribute PDF forms without fear of them being passed on to unauthorized parties.  This is especially useful if your IPR is the form itself and you want to protect revenue generating content from being pirated and misused. It’s also ideal if you want to protect form content from unauthorized disclosure and modification.

Locklizard provides total and secure PDF form distribution and even enables you to encrypt form data on submission for additional security.

Why Locklizard for Secure PDF Forms?

Save fillable PDF as read only: securely lock, distribute & submit PDF forms without passwords

Locklizard provides total PDF form protection with US Gov strength AES encryption and public key technology to ensure your forms, form fields, and data remain protected no matter where they reside.

  • Our DRM PDF Security products enable secure PDF form distribution without insecure passwords or plug-ins, and enforce access, location, expiry, and usage controls.
  • Unlike Adobe Permissions which can be easily removed, our DRM controls persistently protect your PDFforms and enable you to revoke them at any time regardless of where they are located.
  • Secure PDF form submission – form data can be encrypted on submission so that it cannot be modified after the form has been filled out and submitted.  Form data is stored encrypted on the server so that it always remains protected.
  • No keys are exposed to users or interfaces and PDF forms are only ever decrypted in memory (no temporary files are created that could be easily copied) – see our DRM technology.
  • Documents are protected on your computer so there are no unprotected copies uploaded to the cloud where they could be compromized.  Distribute protected PDF forms just like any other PDF file – by email, upload to a website, etc.
  • We don’t use JavaScript so we are not exposed to the multiple AcroForm vulnerabilities.
  • Our easy-to-use administration system provides simple user and document management and unlike passwords, keys are transparently and securely managed for you.

Read our customer testimonials and case studies to see why organizations use Locklizard PDF security to protect PDF forms, lock form fields from editing, distribute & share PDF forms securely, and enable secure PDF form submission.


How do you edit a secured PDF form?

It depends on how it is protected.  If it uses Adobe Acrobat security, you can simply upload the form to any PDF password removal service and modify it.  If instead the form was converted to an image, the best course of action is to run it through Acrobat’s OCR tool to make the content editable again.

In PDF forms protected with Locklizard, users can only enter data in form fields.  They cannot edit any other part of the PDF.  They will be unable to remove editing restrictions or screenshot it to run through an OCR tool.

How do I make a PDF form secure for free?

You can’t.  Good security requires constant assessment and improvement by experts, who do not work for free.  Free PDF from protection tools usually just add easily removable editing restrictions or flatten the PDF into an image, which can be run through an OCR tool to be made editable again.  If you want PDF form protection that works, your best option is a paid PDF DRM solution like Locklizard Safeguard.

Is it possible to secure forms online instead?

No.  There are two ways to secure forms online: by uploading a document to a tool to be protected, and by embedding the form into a webpage.  There are currently no online protection tools that offer security that is not easily bypassed, and uploading your sensitive files to somebody else’s server is not a good idea anyway.

Webpages,are easy to manipulate via the browser’s developer mode, which can be used to modify HTML, CSS, and JavaScript.

Can you protect a fillable form in Microsoft Word?

After you create a fillable form in Word, you can make it read-only.  However, this read-only protection is only designed to prevent accidental editing and can be easily removed.  For more information, see Why you should not password protect a Microsoft Word document.

Does Locklizard let me prevent editing while allowing fields to be filled?

Yes, users cannot edit form content but fields can be filled in.  Form fields remain fillable by default and their contents can only be saved to a separate .xml file so that you can choose whether to import them or not once the form is returned to you.

If you want to stop users from interacting with the form at all (i.e. make it non-fillable), you can flatten it before encryption.

How does Locklizard ensure secure PDF form submission?

Apart from using an HTTPS connection, you can encrypt form fields so that information entered in a secure form is encrypted on submit.  Only those that are authorized at the receiving end will be able to decrypt the form data.

Customer Testimonials