Flatten PDF — Lock Form Fields & Annotations Free Online
Make PDF form fields, annotations, comments, and signatures permanently non-editable — entirely in your browser, with no upload required. Powered by PDF-lib, the tool merges all interactive elements into the static page layer so the PDF looks identical but can no longer be modified. Optionally remove hyperlinks and strip document metadata. Free forever.
Flattening merges interactive elements (form fields, annotations) into the static page content. The result is a "locked" PDF that looks identical but cannot be edited.
Flatten Result
How to Flatten a PDF
Alfreto's PDF Flattener uses PDF-lib — a JavaScript library running entirely in your browser — to parse your PDF and permanently merge all interactive elements into the static page layer. No file is ever sent to any server.
Step 1 — Upload Your PDF
Click Choose PDF or drag and drop your file into the drop zone. Only .pdf files are accepted. Password-protected PDFs cannot be processed — remove the password first using your PDF viewer. The filename and file size are shown immediately after selection.
Step 2 — Choose Flatten Options
Select which elements to flatten or remove:
- Flatten Form Fields (default on) — Converts text fields, checkboxes, radio buttons, dropdowns, and digital signatures into static content. Fields can no longer be typed into, checked, or changed. Current values are permanently preserved in the page.
- Flatten Annotations (default on) — Merges comments, sticky notes, highlights, underlines, strikethroughs, and drawing markup permanently into the page. Reviewers can no longer edit or delete these annotations.
- Remove Hyperlinks (default off) — Strips all clickable link annotations from the document. Visible URL text is retained but links become non-interactive. Useful for printed or archived copies.
- Strip Metadata (default off) — Clears document title, author name, subject, keywords, producer, and creator fields. Useful for privacy when sharing documents externally.
Step 3 — Flatten and Download
Click Flatten PDF. A progress bar tracks each stage: loading the PDF, processing form fields, processing annotations page by page, applying metadata options, and saving. When complete, the result panel shows: total pages, number of form fields flattened, annotations removed, and output file size. Click Download to save the flattened PDF — it is named yourfile_flattened.pdf automatically.
When Should You Flatten a PDF?
- Submitting completed forms — Flatten before sending a filled-in application, contract, or registration form to prevent recipients from altering your responses.
- Locking signed documents — Flatten after applying a digital or drawn signature to prevent the signature from being removed or the content from being changed.
- Archiving reviewed documents — Flatten a document after review to lock comments and markup into the page for a permanent, clean record.
- Ensuring consistent rendering — Flatten to prevent fonts, layouts, or form field values from rendering differently in various PDF viewers.
- Printing preparation — Remove hyperlinks and interactive elements before sending to a print service to avoid compatibility issues.
- Privacy-sensitive sharing — Strip metadata before sharing externally to remove author name, revision history, and other embedded document properties.
Frequently Asked Questions
Is my PDF uploaded to a server when I flatten it?
No — your PDF never leaves your device. The tool uses PDF-lib, a JavaScript library running entirely inside your browser tab. No data is sent over the internet at any point. This makes it completely safe for confidential documents such as contracts, signed agreements, medical forms, and financial statements.
What does "flattening" a PDF actually mean?
Flattening merges all interactive or overlay elements — form fields, checkboxes, radio buttons, text annotations, comments, sticky notes, highlights, and signatures — permanently into the underlying static page content. The PDF looks visually identical after flattening, but none of these elements can be edited, deleted, or interacted with anymore. They become part of the page itself, like printed text.
Will the visual appearance of the PDF change after flattening?
No. The PDF will look exactly the same after flattening. Text field values, checkbox states, dropdown selections, annotation content, and signature appearances are all preserved — they just become static page content rather than interactive elements. What you see before flattening is what you get after flattening.
Can I undo or unflatten a PDF after flattening?
No. Flattening is a permanent and irreversible operation. Once interactive elements are merged into the page layer, they cannot be separated or restored. Always keep a copy of the original unflattened PDF before running this tool.
What is the difference between flattening form fields and flattening annotations?
Form fields are interactive input elements built into the PDF structure — text boxes, checkboxes, radio buttons, dropdowns, and signature fields. Annotations are overlay elements added by reviewers — comments, sticky notes, text highlights, underlines, strikethroughs, and drawing markup. Both types are interactive and editable by default; flattening makes them permanent. You can choose to flatten one without the other using the separate checkboxes.
Why would I remove hyperlinks when flattening?
Removing hyperlinks is useful when: you are preparing a document for printing (where links serve no purpose), you want to distribute a document without recipients being directed to external websites, or you need to submit a form to a system that does not support PDF link annotations. Visible URL text is preserved as plain text — only the clickable link behavior is removed.
What metadata does the Strip Metadata option remove?
Stripping metadata clears the document's title, author name, subject, keywords, producer, and creator fields. These fields are embedded in the PDF and are not visible on the page, but can be read by PDF viewers, search engines, or metadata analysis tools. Stripping them is recommended when sharing documents externally for privacy reasons.
Can I flatten a password-protected PDF?
No. Encrypted or password-protected PDFs cannot be processed by PDF-lib without the correct password, and the tool will show an error. You need to remove the password first. In Adobe Reader, Preview (Mac), or Chrome's PDF viewer, open the file, enter the password, then save or print to PDF without a password before flattening.
Why Use Alfreto to Flatten PDFs?
Most online PDF flattening tools upload your document to a remote server, which creates a privacy risk for confidential content. Alfreto's flattener runs entirely in your browser — no upload, instant processing, and completely free with no limits.