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CALCPARK

PDF Editor

Edit a PDF in your browser: add text, images, boxes, lines and highlights, delete, rotate and reorder pages, then save. No upload; existing text is not editable.

Files stay on your device
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How to use it

  1. Drop the PDF. Page thumbnails appear on the left; click one to edit it.
  2. Pick a tool: Text (click, type, Enter), Rectangle / Line / Highlight (drag), or Insert image. Switch back to Select to move, resize, rotate or delete an object (Delete key).
  3. Use Rotate 90°, Move up/down and Delete page for page-level changes.
  4. Press “Save PDF” and download. The source file is never modified; save again after further edits.

Example

A 6-page contract: delete the blank page 6, rotate the landscape appendix on page 5 to upright, type “APPROVED 2026-10-19” in red 18 pt on page 1 and draw a box around the amount on page 3. Saving produces a 5-page PDF about 4 KB larger than the original: the text is one Tj operation with the Helvetica-Bold standard font, the box is a re S path. The text can be found with Ctrl+F in any viewer.

How the editor works

pdf.js renders the current page at 1.5 px/pt onto a canvas that becomes the background of a Konvastage. Objects are stored in display coordinates (points, top-left origin, after the page’s rotation). On save, pdf-lib copies the pages in their new order, sets each page’s /Rotate, and converts every object into user-space coordinates (bottom-left origin, before rotation) with the inverse of the display transform; text and images rotated on screen receive the matching counter-clockwise angle. Highlights are drawn with the Multiplyblend mode at 45 % opacity so the text underneath stays legible.

Limits

  • No editing of existing text, images or form fields; no OCR.
  • No undo history yet – delete an object and re-create it, or reload the file.
  • Images are placed at their pixel size scaled to 40 % of the page width; PDF-internal compression is not applied beyond what PNG/JPEG already provide.
  • Pages are rendered one at a time; very large scans may take a second to appear when switching pages.

Sources: pdf-lib – PDFPage drawing API, PDF 32000-1:2008 – 8.3 Coordinate systems, 11.3.5 Blend modes, Konva – Transformer.

Questions

Can I change the text that is already in the PDF?
No. PDF stores text as positioned glyphs without flow, and reliable in-place editing needs the original fonts. Cover the old text with a white filled rectangle and type the new text over it, or convert the PDF to Word, edit, and convert back.
Is the added text selectable in the saved file?
Yes, for Latin-1 text: it is written with the standard Helvetica fonts. Text with other scripts is embedded as a high-resolution transparent image, which looks the same but cannot be selected.
Why do objects move when I rotate a page?
They do not move relative to the page content: rotating turns the page and everything on it together, so a box around a paragraph stays around that paragraph.
Does this sign documents?
Use the PDF Sign tool for signatures – it has a drawing pad, typed signatures, image upload and date stamps. Neither tool creates a cryptographic (digital certificate) signature.