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TrueScalers

Edit a PDF and sign it

A PDF editor changes an existing document rather than creating one. This editor edits text in place, adds new text boxes, and applies a drawn or uploaded signature, then writes a real PDF. A signature placed 200 points from the left edge is written at exactly 200 points, at any zoom level, because positions are stored in PDF points rather than screen pixels.

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How to edit and sign a PDF

  1. 01

    Open your PDF

    Drag a PDF onto the drop zone or click to choose one. The document opens in the editor with page thumbnails, and nothing is sent anywhere.

  2. 02

    Edit the text that is already there

    Choose Edit text and click any line. The editor matches the closest available font, keeps the original size and colour, and lets you retype the line.

  3. 03

    Add text and a signature

    Use Add text to place a new text box anywhere, then Signature to draw one with a mouse, finger or stylus, or upload a PNG, JPG or WebP image.

  4. 04

    Position everything

    Drag objects to move them, use the corner handles to resize, and the round handle above an object to rotate it. Ctrl+Z undoes any step.

  5. 05

    Save the finished PDF

    Press Save PDF. The original pages are copied rather than re-rendered, so text stays selectable and image quality is unchanged.

The formula

user_x = display_x + crop_x;    user_y = crop_y + crop_height − display_y    (unrotated page)
display_x
Distance in points from the left edge of the page as it appears on screen.
display_y
Distance in points from the top edge of the page as it appears on screen.
crop_x
The x coordinate of the page crop box, which is zero for most documents.
crop_y
The y coordinate of the page crop box, which is zero for most documents.
crop_height
The height of the page crop box in points, at 72 points to the inch.
user_x
The x coordinate written into the PDF, measured from the bottom-left corner.
user_y
The y coordinate written into the PDF, measured from the bottom-left corner.

PDF measures from the bottom-left corner and a screen measures from the top-left, so every placement is converted once, at save time. Zoom never appears in the conversion: an object is stored in points, and zoom only changes how many screen pixels a point occupies. That is why an element placed at 400% magnification lands in the same spot as one placed at 50%. Pages carrying a /Rotate entry of 90, 180 or 270 degrees use the corresponding rotation of the same transform.

Worked example

Page
US Letter — 612 × 792 points
Signature placed at
200 pt from the left, 560 pt from the top
Signature size
120 × 60 points
Editor zoom
175%
Result
Written at x = 200, y = 172 in PDF coordinates

The signature box starts 560 points below the top of the page and is 60 points tall, so its bottom edge sits 620 points down. PDF coordinates run upward from the bottom-left corner, so that bottom edge is 792 − 620 = 172 points above the bottom of the page. The horizontal coordinate is unchanged at 200 points. The editor was at 175% magnification, which means the box measured 210 by 105 screen pixels, but zoom is divided out the moment the pointer is released, so the saved position is 200, 172 regardless.

Frequently asked questions

Can you edit the existing text in a PDF?

Yes, with one honest caveat. A PDF stores positioned glyphs rather than editable paragraphs, so this editor reads the position, size and colour of a line, covers the original with a matching background fill, and draws the replacement on top. The result reads as an edit and keeps the surrounding layout, but the original characters remain in the file beneath the cover.

What happens when the original font is not available?

The closest of the fonts built into every PDF reader is chosen automatically. Arial, Calibri, Segoe UI and similar faces map to Helvetica; Georgia, Cambria and Garamond map to Times; Consolas and Menlo map to Courier. Bold and italic are read from the original font name, so a bold heading stays bold. Character widths differ slightly from the original face.

Does the signature stay sharp when it is resized?

A drawn signature does, because the strokes are stored as vector paths and written to the PDF as path operators rather than pixels. Enlarging it on a printed page keeps the edges crisp at any size. An uploaded signature is a photograph or scan, so it has a fixed resolution and behaves like any other image when scaled beyond it.

Will a signature appear exactly where it was placed?

Yes. Every object is stored in PDF points measured from the top-left of the page, and the browser zoom level is divided out the moment a pointer is released. Placing a signature at 400% magnification, at 50%, on a phone or on a wide monitor all produce the same coordinates in the saved file, on any page of a multi-page document.

Does editing a PDF reduce its quality?

No. The original pages are copied into the new document with their content streams intact rather than being rendered to images. Embedded fonts stay embedded, vector graphics stay sharp at any zoom, photographs keep their original compression, and text elsewhere on the page stays selectable and searchable. Only the specific rectangle behind an edited line is painted over.

Can pages be rotated, deleted or reordered?

Yes. The thumbnail rail on the left rotates a page in quarter turns, deletes one, or moves one up and down the running order, by dragging or with the arrow buttons for keyboard use. A deleted page is marked rather than discarded and can be restored, and every page operation is covered by undo.

Is an uploaded signature image sent to a server?

No upload occurs anywhere in this tool. The PDF and the signature image are both read from local disk into browser memory, edited by JavaScript running in this page, and written back out as a download. This site has no server-side code that could receive a file, so a signed contract stays on the device it was signed on.

Which characters can be typed into an edited PDF?

The fonts built into every PDF reader cover the Windows-1252 range, which includes English, most Western European languages, accented letters, curly quotes and the euro and pound signs. Characters outside that range, such as Cyrillic, Greek, Chinese, Japanese, Korean and emoji, cannot be written, and the editor names the exact character rather than dropping it silently.

Sources

Last reviewed: · Formula and sources verified by Syed Aqeel Ahmad Gillani. See the methodology for how every calculation is derived.

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