Flatten PDF Free: Files Without Form Fields Save Unchanged
Free Tool Tests • Flatten PDF Free: Files Without Form Fields Save Unchanged
💡 Summary
Flattening a PDF locks form fields, comments, and stamps into the page with no sign-up or watermark. The tool runs directly inside your web browser so your files are never uploaded to a server. Across 15 test cases, all valid files processed properly while invalid files were safely rejected.
Key Metrics & Specifications
| Tool | Free Flatten PDF: Lock Form Fields, Comments and Stamps |
| Tested | 2026-11-03 · Chromium (desktop) · free version |
| Test cases passed | 15 of 15 |
| Tool page | https://avaloncompany.ai/tools/flatten-pdf/ |
What we ran through the tool
15 of 15 cases behaved correctly · 2026-11-03 · Chromium (desktop) · free version
| Input | Type | What the tool did |
|---|---|---|
| a typical file | Typical file | PDF file, 3 pages “2.5 KB · Nothing to flatten: this PDF has no form fields, comments or stamps. Saved unchanged.” |
| as pictures | Typical file | PDF file, 3 pages “457.9 KB · 3 pages saved as pictures” |
| a very long file name | Tricky file | PDF file, 3 pages “2.5 KB · Nothing to flatten: this PDF has no form fields, comments or stamps. Saved unchanged.” |
| a file name with extra spaces and an emoji | Tricky file | PDF file, 3 pages “2.5 KB · Nothing to flatten: this PDF has no form fields, comments or stamps. Saved unchanged.” |
| a file name with Korean and Japanese characters | Tricky file | PDF file, 3 pages “2.5 KB · Nothing to flatten: this PDF has no form fields, comments or stamps. Saved unchanged.” |
| a 1-byte PDF file | Tricky file | Not processed “pdf_1byte.pdf is not really a PDF: its contents are in a different format, so it was not added.” |
| a password-protected PDF | Tricky file | Not processed “This PDF is locked. Remove the password with the unlock PDF tool first, then flatten the unlocked copy.” |
| a JPEG file renamed to look like a PDF | Tricky file | Not processed “pdf_fake.pdf is not really a PDF: its contents are in a different format, so it was not added.” |
| a PDF with pages of different sizes | Tricky file | PDF file, 3 pages “2.5 KB · Nothing to flatten: this PDF has no form fields, comments or stamps. Saved unchanged.” |
| a PDF with Korean, Japanese, Chinese, Arabic, Hindi, Thai and Russian text | Tricky file | PDF file, 2 pages “42.2 KB · Nothing to flatten: this PDF has no form fields, comments or stamps. Saved unchanged.” |
| a scanned, image-only PDF | Tricky file | PDF file, 1 page “25.0 KB · Nothing to flatten: this PDF has no form fields, comments or stamps. Saved unchanged.” |
| a cut-off (truncated) PDF file | Tricky file | Not processed “This file is not a valid PDF or it is damaged.” |
| an empty (0-byte) PDF file | Tricky file | Not processed “pdf_zero.pdf is empty (0 bytes), so it was not added.” |
| a batch 1 MB over the free size limit | Free limit | Not processed “pdf_mb_101.pdf was not added: the limit is 100 MB.” |
| 2 files (one over the free limit) | Free limit | Not processed “The free version flattens one PDF at a time, so only the first one you chose was used.” |
“Behaved correctly” means the tool produced a valid output file we reopened and checked, or refused the input with a clear message. Open the tool.
Try it on your own file
The same free tool we tested above. No sign-up.
Internal link to avaloncompany.ai.
How to flatten a PDF step by step
Drop your PDF file into the tool on the page. You do not need to register an account, and the output has no watermark.
Choose your flattening method. Selecting forms, comments, and stamps into the page keeps text sharp, searchable, and file size small. Selecting every page into a picture fixes all text so nothing can be selected, creating a larger file.
Press Flatten PDF to process the document. The operation runs entirely inside your browser on your own device, and you download the updated PDF immediately.
How we tested the free flattening tool
On 2026-11-03, we ran 15 automated test cases using a desktop Chromium browser on the free tier.
All 15 tests passed. The suite evaluated standard 3-page documents, files with mixed page dimensions, image-only scans, and multi-language files containing Korean, Japanese, Chinese, Arabic, Hindi, Thai, and Russian text.
We also tested edge cases such as long file names, emojis, corrupted files, password-locked documents, and uploads exceeding free limits.
Handling invalid, damaged, and protected files
When a document contains no interactive elements, the tool avoids unnecessary changes. A standard 3-page test file returned: "2.5 KB · Nothing to flatten: this PDF has no form fields, comments or stamps. Saved unchanged."
If a file is password-protected, the tool rejects it with the prompt: "This PDF is locked. Remove the password with the unlock PDF tool first, then flatten the unlocked copy."
Non-PDF files and damaged data are caught before processing. A 1-byte file returned: "pdf_1byte.pdf is not really a PDF: its contents are in a different format, so it was not added." A renamed JPEG file produced the same message.
An empty file showed: "pdf_zero.pdf is empty (0 bytes), so it was not added." A cut-off or truncated file displayed: "This file is not a valid PDF or it is damaged."
Free tier limits and when not to use this tool
The free version is limited to one PDF at a time with a maximum file size of 100 MB.
When two files were chosen together, the tool reported: "The free version flattens one PDF at a time, so only the first one you chose was used." A 101 MB file triggered: "pdf_mb_101.pdf was not added: the limit is 100 MB."
Do not use this tool to remove private names or numbers. Flattening fixes what is visible so it cannot be moved or deleted, but it does not redact information. To remove sensitive text permanently, use a redact PDF tool instead.
We re-run these tests when the tool changes. Results describe this tool on the date shown.
Frequently Asked Questions (FAQ)
Q. Does flattening a PDF remove private information?
No. Flattening only locks visible content into the page. It does not erase data. To remove sensitive text or numbers permanently, use a redact PDF tool.
Q. Are my files uploaded to your servers?
No. The PDF is flattened entirely inside your browser on your own device. Nothing is sent to external servers.
Q. What is the difference between the two flattening options?
Flattening forms, comments, and stamps keeps text sharp and searchable while keeping the file small. Flattening every page into a picture turns all page content into an image so no text can be selected, but it increases the file size.
Try it on your own file
The same free tool we tested above. No sign-up.
Internal link to avaloncompany.ai.