Watermark PDF adds a diagonal text overlay across all pages — useful for marking drafts, confidential documents, and sample files. Enter the watermark text, adjust the font size and opacity, and download the watermarked PDF instantly. All processing happens in your browser using pdf-lib — your file is never uploaded to a server. Free, no account needed.
Related: MergeCompressOrganize
Your files and inputs stay in your browser — nothing is uploaded or stored.
Watermark PDF Add a diagonal text watermark across all pages — opacity control. It lives in DevBench's PDF collection — open it in any modern browser with JavaScript enabled. There is no install step and no account wall: you get the UI immediately so you can paste input, tweak options, and copy output during real debugging sessions.
Like the rest of DevBench, this workflow runs entirely in your browser by default. Your text and files are processed with client-side JavaScript, which means they are not sent to our servers for routine formatting or conversion — open DevTools → Network and you should see no upload when you use the core controls. That makes these tools practical for internal payloads, configs, and drafts when you want to avoid unnecessary cloud round-trips.
Start from the controls above: paste or type into the labelled fields, upload when the tool supports files, and watch results update as you work. If output looks unexpected, verify encoding (UTF-8), line endings, and whether the tool expects structured input such as JSON, YAML, CSV, or hex. Many utilities include copy buttons or downloadable results so you can drop answers straight back into tickets, CI logs, or documentation.
If you need deterministic automation at scale, shell scripts and CI pipelines still win — use DevBench to prototype the transform and validate edge cases, then port the same logic into your stack when you are happy with the behaviour.