How to edit a PDF

Short answer: open the PDF in Omni PDF's browser editor, use the left sidebar to add or modify content, then click Download to save a new PDF. Everything runs in your browser — the file doesn't leave your device.

PDF is a fixed-layout format. Unlike a Word document, the content on a PDF page is positioned glyph by glyph, so "editing" a PDF usually means adding new elements on top of the page rather than rewriting paragraphs in place. This guide covers what you can realistically do and how to do it well.

What you can edit in a PDF

Most PDF editors, including Omni PDF, work in the "additive" model:

• You can add text boxes, images, shapes, arrows, signatures, highlights, underlines, strike-throughs, comments, checkboxes and links.
• You can change page properties: rotation, order, duplication, deletion, insertion of blank pages, cropping and watermarks.
• You can't reliably edit a PDF's existing text runs or move its original objects — that depends on the document and is intentionally not exposed because it can silently corrupt a file.

The approach: add a text box over the region you want to change, and hide the underlying content with a white rectangle if needed. This works for the vast majority of real-world tasks — filling forms, correcting a line, adding notes, signing contracts.

1. Open your PDF

Go to /editor/ and either drop a PDF onto the canvas or use Choose PDF. The file loads locally. You'll see thumbnails of every page and the canvas will show the first page rendered at 100%.

2. Add and edit text

Select the Text tool from the left sidebar (T). Click anywhere on a page to place a text box. Start typing.

To style the text, use the properties panel on the right:

• Size — font size in points
• Color — text color
• B and I — bold and italic toggles
• Align — left, center, right
• Opacity — 0 to 1

Click any existing text box with the Select tool (V) to reopen the properties panel for that box. Delete it with the trash icon or press Delete.

3. Insert and resize images

Pick the Image tool and click on the page. You'll be asked to choose an image file. It's inserted at the click point with its natural size. Drag the corner handles to resize; drag inside the image to move it.

Supported formats depend on the browser, but JPEG and PNG are universal.

4. Draw shapes and arrows

Use Shape to draw rectangles, ellipses and lines. Use Arrow to add directional callouts — useful for reviewing screenshots or pointing at contract clauses.

Drag from the start point to the end point. On release, the shape is committed to the page and appears in the properties panel, where you can set stroke color, fill, width and opacity.

5. Annotate pages

Highlight, underline and strike-through work by dragging a rectangle over the text region you want to mark. Use Comment to add a pinned note, and Checkbox for fillable form-like elements.

Draw (D) lets you sketch freehand with your mouse, finger or stylus — useful for signatures, checkmarks and quick corrections.

6. Rotate, reorder and delete pages

Click the Pages tool in the sidebar (or the page thumbnails panel) to see a compact list of every page. From here you can:

• Rotate any page by 90°
• Delete a page entirely
• Duplicate a page
• Insert a blank page after any page

To merge another PDF into the document, use Merge PDF. To extract a range of pages, use Split PDF or the page-organize tool.

7. Export a valid PDF

Click Download in the top right. The editor flattens every annotation into the page content, applies rotations, reorders pages as needed and produces a valid PDF that opens in any reader — Adobe Acrobat, Preview, Chrome, Firefox, mobile apps.

8. Limitations to know

• Encrypted PDFs. Password-protected files need to be unlocked first. The editor will tell you if a file can't be opened.
• Original text editing. You can cover and replace text, but the original text run isn't rewritten in place.
• Form fields. Existing AcroForm fields aren't editable as live fields — you can add your own visual form elements.
• Very large files. Processing is local, so a 200 MB PDF on a low-end phone will be slow.

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