Muffin's PDF Studio
Fill PDF forms, add your signature, and crop pages — entirely in your browser. No uploads, no account, no data shared. Ever.
What is Muffin's PDF Studio?
Muffin's PDF Studio is a free, browser-based PDF editor with four tools in one place — fill PDF forms, add digital signatures, place tick marks and strikethroughs, and crop PDF pages. Everything is processed locally in your browser using PDF-lib and PDF.js. Your contracts, salary slips, government forms, and signed documents never leave your device — no account, no upload, no server.
How to fill a PDF form without uploading it
Go to the Fill & Sign tab and upload your PDF. Make sure T Text box mode is selected in the toolbar. Set your preferred font, size, and color. Then drag on any blank field on the PDF page to draw a text box — it appears exactly where you drew it. Type your content inside. Drag the thin handle bar at the top to reposition it anywhere, and drag the bottom-right corner to resize. Once you are happy with all entries, click Download PDF — your filled form downloads instantly with all text permanently embedded.
How to add a digital signature to a PDF
Go to the Signature tab. Two options — draw your signature directly on the canvas using mouse or touchscreen, or upload a photo of your handwritten signature on white paper. When you upload a photo, Muffin removes the white background automatically using pixel brightness thresholding, leaving only the ink as a transparent PNG. Use the threshold slider to fine-tune the extraction until it looks clean.
Click Save as PNG to download your extracted signature for future use — so you never have to re-draw it. Load your PDF, click once anywhere on the page to place the signature instantly, drag it to the right position, resize using the green corner handle, and hover to reveal the × delete button. Download your signed PDF when done.
How to use tick marks and strikethroughs
In the Fill & Sign tab, the toolbar has three modes. Switch to ✓ Tick mark and click anywhere on the PDF to stamp a checkmark — useful for marking options on forms, ticking boxes, or annotating a document for review. The tick size and color follow your current toolbar settings.
Switch to S̶ Strikethrough and drag horizontally across any text or field to draw a line through it — useful for marking entries as void, crossing out incorrect values, or showing changes on a reviewed document. Drag to move, drag the right edge to extend or shorten. Both tick marks and strikethroughs are fully embedded into the downloaded PDF.
How to crop a PDF page
Go to the Crop PDF tab. Upload your PDF and drag on the page to draw a rectangle around the area you want to keep — the surrounding area turns dark so you can see exactly what will be removed. Choose whether to apply the crop to the current page only or to all pages at once. Click Apply crop, then download. This is useful for removing oversized blank margins from scanned documents, stripping headers or footers, or trimming a PDF to a specific region before sharing.
Your PDF never leaves your browser
Most popular online PDF editors require account creation and upload your file to their cloud servers — meaning your salary slips, academic certificates, government forms, and signed contracts are stored on someone else's infrastructure. Muffin's PDF Studio processes everything locally using PDF-lib for editing and PDF.js for rendering. Close the browser tab and there is no trace of your document anywhere. No account, no file size limit, no watermark added to your output.