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PDF SealBox
PDF SealBox — Stamp, sign, number and organise PDF pages in your browser.
About PDF SealBox
PDF SealBox is a browser-based toolkit for everyday PDF workflows. Add visible text or image stamps, signature images, approval marks, cross-page seals, page numbers and watermarks. You can also convert images to PDF, split PDFs, or export selected pages as JPG or PNG. Preview the result and download a separate file. It is designed for document preparation and office workflows; visible marks are not certificate-backed digital signatures or legal certification.
- Who it is for
- People and small teams preparing PDFs for routine office review, approval, filing, and sharing.
- Problem it solves
- Adding a visible mark or page numbers to a PDF can lead people to print, stamp, scan, and re-file the document, or switch between several separate tools. That adds steps and makes it harder to keep page order and output consistent.
- The solution
- Choose the task, select pages and settings, preview the result, then download a separate output file. The source file remains unchanged. Supported browser workflows process files locally; available controls can vary by tool and browser.
- What makes it unique
- PDF SealBox combines focused workflows for visible text and image stamps, cross-page seals, page numbers, watermarks, image-to-PDF conversion, splitting, and page-to-image export. It is for practical document preparation and does not create certificate-backed digital signatures or legal certification.
Features
Convert images to PDF
Convert PDF pages to images
Split PDF by pages or ranges
Add page numbers to a PDF
Add a visible PDF stamp
Add a watermark to a PDF
Details
- Platforms
- Web
- Pricing
- Free
- Built for
People and small teams preparing PDFs for routine office review, approval, filing, and sharing.
- Building since
2026
Technology
Website performance
Recorded mobile lab measurements and finalized weekly standings from IndieTools Speed.
PDF SealBox website speed overview
94
Performance scoreGood
In IndieTools' mobile lab test on November 11, 2026, the PDF SealBox website scored 94 out of 100 (good). Largest Contentful Paint took 952 ms, rated good.
Measured (UTC)
- LCPLargest Contentful Paint
- 952 ms
- Good
- TBTTotal Blocking Time
- 261 ms
- Needs improvement
- CLSCumulative Layout Shift
- 0.000
- Good
- FCPFirst Contentful Paint
- 952 ms
- Good
Not ranked in a finalized week yet.
PDF SealBox lab metrics
| Metric | Result | Status | Trend |
|---|---|---|---|
| Mobile lab testMid-range phone on a throttled 4G connection, two runs averaged. Changes compare with the run on Nov 10. | |||
| Performance score GoodUp 9 points | 94 / 100 | GoodUp 9 points | |
| First Contentful Paint GoodAbout the same | 952 ms | GoodAbout the same | |
| Largest Contentful Paint GoodAbout the same | 952 ms | GoodAbout the same | |
| Speed Index Needs improvement905 ms faster | 3.55 s | Needs improvement905 ms faster | |
| Total Blocking Time Needs improvement220 ms faster | 261 ms | Needs improvement220 ms faster | |
| Cumulative Layout Shift GoodAbout the same | 0.000 | GoodAbout the same | |
| Unthrottled observationsTimed on the test machine's own fast connection, so they read lower than the lab metrics above. | |||
| Page load 712 ms faster | 2.78 s | 712 ms faster | |
| Server response About the same | 3 ms | About the same | |
PDF SealBox performance history
3 comparable mobile lab runs since November 10, 2026. Choose a metric and a range, then move along the line to read each run.
PDF SealBox Speed ranking
Not ranked yet. Ranks appear once a week with this product is finalized.
Stored lab observations from controlled test runs, not real-user Core Web Vitals or a guarantee of search rankings. Weekly standings remain attached to their finalized edition.Method psi-mobile-two-sample-mean-v1, 2 samples per reading. Lab results can vary between runs.
Domain Rating
Domain Rating by Ahrefs- DR4 (primary model)
- 0
No change since 10 Nov
- DR3
- 2
No change since 10 Nov
Model difference−2. DR4 is 2 points lower than DR3.
Measured · pdfsealbox.com
What do DR4, DR3 and the model difference mean?
- DR4:
- Ahrefs' newer model. It gives more weight to links from sites with organic search traffic and rates a subdomain on its own links.
- DR3:
- The previous model, shown in the Ahrefs app until 1 December 2026.
- Model difference:
- DR4 minus DR3 for the same domain. The models calculate differently, so this is not growth or a drop; the “since” lines compare each model with itself.
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