PDF Signer — Add Signature & Chop Overlays Online
Drop signature and company chop images onto any PDF — fully in your browser, no upload.
这个工具是做什么的
PDF Signer is a free browser-based tool for adding signature and stamp (chop) overlays to PDFs. Drop in a PDF, upload one or more PNG or JPG images (transparent backgrounds preserved), then drag, resize, and rotate them onto any page. When you're done, download a flattened, ready-to-send PDF.
It is built for people who need to sign contracts, stamp invoices, mark up forms, or counter-sign agreements without uploading the original document to a third-party server. The PDF and your signature image bytes never leave your device — all of the editing and PDF assembly happens in JavaScript inside your browser tab.
PDF Signer works on desktop and mobile. Touch, mouse, and pen input all use the same Pointer Events code path, so dragging and resizing feel the same on a phone as on a laptop.
使用方法
- Drop your PDF onto the dropzone (or click to choose a file).
- Upload your signature or chop as a PNG (transparent background recommended) or JPG.
- Click the image in the sidebar to place it on the current page.
- Drag to move; drag the corner handle to resize; drag the top handle to rotate.
- Switch pages from the sidebar and place as many overlays as you need.
- Click 'Download signed PDF' to save the finished file to your device.
Common use cases
- Signing contracts, NDAs, quotations, and invoices.
- Stamping a company chop on letters, vouchers, and receipts.
- Adding initials to school or HR forms.
- Approving multi-page reports without printing them.
- Counter-signing offer letters and onboarding documents.
What it can handle
- Multi-page PDFs up to 50 MB.
- Transparent PNG signatures (alpha is preserved as a PDF soft mask).
- Opaque JPG company chops.
- Multiple overlays across multiple pages in a single session.
- Rotation and uniform scaling of every overlay.
常见问题
Is my PDF uploaded anywhere?
No. Files are read by your browser, edited in memory, and downloaded back to your device. Nothing is sent to any server.
Does it work with password-protected PDFs?
Not directly. Unlock the PDF first (using Acrobat, Preview, or any unlock tool), then drop the unlocked copy here.
Will my signature stay transparent?
Yes. If you upload a PNG with a transparent background, the transparency is preserved when the image is embedded into the PDF.
Can I add the same signature to every page?
Yes. Place it on one page, switch pages with the sidebar, and click your signature in the library again to add another copy.
Will it invalidate digital signatures already on the PDF?
Yes — any modification to a digitally signed PDF will invalidate the cryptographic signature. Use this tool only on documents that have not been digitally signed.
What's the maximum PDF size?
50 MB. Browser memory limits make larger files unreliable on phones and entry-level laptops.
Will the signature stay editable after I download the PDF?
No — overlays are flattened into the page, so they look the same in any PDF viewer and can't be moved or removed by the recipient.
Does it work on mobile?
Yes. The editor uses Pointer Events, which means touch input works the same as mouse input. The sidebar reflows for narrow screens.