How to Edit a PDF Online: Add Text, Images, and Annotations

PDF Editing: Setting Realistic Expectations

PDF was never designed to be edited. That is not a flaw -- it is the entire point. PDF (Portable Document Format) exists to preserve a document's exact appearance, making it look identical on every screen, printer, and device. The fixed-layout architecture that makes PDFs universally reliable is the same architecture that makes editing them fundamentally difficult.

This matters because the phrase "edit a PDF" means very different things to different people. If you need to add a text note, insert an image, highlight a passage, or fill in a form field, online PDF editors handle these tasks well. If you need to rewrite paragraphs, restructure content, or change the layout, you are better off converting the PDF to a DOCX file, making your changes in a word processor, and converting back.

Understanding this distinction saves time and frustration. This guide covers what online PDF editing can do well, what it cannot do, and the tools and techniques for each type of modification.

What You Can Do: Types of PDF Edits

Adding Text

Adding new text to a PDF is the most common editing need. You want to fill in a date, add a note, type a response, or insert a label. Online PDF editors create a text overlay -- a new text element positioned on top of the existing page content.

Using the PDF editor on ConvertIntoMP4:

1. Upload your PDF to the editor
2. Select the Text tool from the toolbar
3. Click anywhere on the page to place a text box
4. Type your text
5. Adjust the font, size, and color to match the surrounding content
6. Position the text precisely using drag-and-drop or arrow keys
7. Save and download the edited PDF

The added text sits on top of the original page content. Visually, it blends in. Structurally, it is a separate element. This distinction rarely matters for practical purposes, but it means the added text may behave slightly differently from the original text in certain scenarios (like text selection or copy-paste).

Modifying Existing Text

This is where expectations need to be tempered. Editing existing text in a PDF is limited compared to editing in a word processor:

If your edit is small -- changing a date, fixing a typo, updating a phone number -- the PDF editor handles it. The text tool in the PDF editor can select and replace individual words or short phrases.

If your edit is substantial -- rewriting paragraphs, adding sections, changing the document structure -- convert to DOCX first using the DOCX converter. Our guide on how to convert PDF to Word covers the best practices for this workflow.

Adding Images and Logos

Inserting an image into a PDF is useful for adding a company logo to a letterhead, placing a photo in a form, inserting a chart or diagram, or adding a stamp or seal.

Steps using the online PDF editor:

1. Upload your PDF
2. Select the Image tool
3. Upload the image file (JPG, PNG, or SVG)
4. Position the image on the page using drag-and-drop
5. Resize by dragging the corner handles
6. Adjust layering if the image should appear behind text

For logos and stamps that need a transparent background, use a PNG file with an alpha channel. JPG images will have a solid background that covers whatever is beneath them. For help with image formats, see our guide on PNG vs JPG: when to use each.

Annotations: Highlights, Underlines, and Comments

Annotations are the bread and butter of PDF editing -- the area where PDF editors truly excel, because annotations were built into the PDF specification from the beginning.

Highlight: Select text and apply a colored highlight (yellow, green, blue, pink). Useful for reviewing documents, marking important passages, and preparing study materials.

Underline and Strikethrough: Mark text with underline or strikethrough formatting. Strikethrough is commonly used in legal document review to indicate proposed deletions.

Comments and Sticky Notes: Add comment boxes that can be placed anywhere on the page. Click to expand them and read the full comment. These are essential for document review workflows.

Drawing Tools: Freehand drawing, lines, arrows, rectangles, circles, and other shapes. Use these to circle important areas, draw attention to specific content, or add visual markup.

Form Filling

Many PDFs include interactive form fields -- text inputs, checkboxes, radio buttons, and dropdown menus. These are designed to be filled in, and any PDF editor handles them:

1. Open the PDF in the editor
2. Click on a form field
3. Type your response or select an option
4. Tab to the next field
5. Save the filled form

If the form is a "flat" PDF (it looks like a form but has no interactive fields), you will need to use the text tool to type your responses in the appropriate positions. This is common with government forms and older documents that were scanned rather than created digitally.

Signature Placement

Adding a signature to a PDF is one of the most frequent editing needs. The sign PDF tool on ConvertIntoMP4 offers three methods:

• Type: Enter your name, rendered in a signature-style font
• Draw: Use your mouse, trackpad, or touchscreen to draw your signature
• Upload: Upload an image of your handwritten signature

Each method produces a signature that can be positioned and sized on any page of the document. For a complete walkthrough of the signing process, legal considerations, and signature types, see our guide on how to sign a PDF online.

Adding Watermarks

Watermarks -- text or images overlaid on every page -- serve as branding, confidentiality markers, or draft indicators. Common watermarks include "CONFIDENTIAL," "DRAFT," "SAMPLE," and company logos.

Adding a watermark to a PDF involves placing a semi-transparent text or image element that appears on every page (or selected pages). For detailed instructions on watermark placement, opacity settings, and positioning, see our guide on how to add a watermark.

Step-by-Step: Common Editing Workflows

Workflow 1: Fill and Sign a Form

This is the most common PDF editing task. You receive a form that needs your information and signature.

1. Upload the PDF to the PDF editor
2. Fill in all text fields (use the Tab key to navigate between fields)
3. Check appropriate checkboxes
4. Switch to the sign PDF tool and add your signature
5. Download the completed form

Workflow 2: Review and Annotate a Document

You are reviewing a document and need to provide feedback.

1. Upload the PDF
2. Use the Highlight tool to mark important passages
3. Add Sticky Notes with comments at specific points
4. Use Strikethrough to indicate text that should be removed
5. Use the Text Box tool to suggest replacement text
6. Draw arrows to connect related items
7. Save and send the annotated PDF back to the author

Workflow 3: Add a Logo to Every Page

You need to brand a document with your company logo.

1. Upload the PDF
2. Add the logo image to the first page
3. Position and size it appropriately (typically top-right or top-left corner)
4. Apply the logo as a watermark to all pages if the tool supports it
5. Download the branded document

Advanced Editing Techniques

Redacting Sensitive Information

Redaction permanently removes content from a PDF -- blacking out names, social security numbers, financial figures, or other sensitive data. True redaction is different from drawing a black rectangle over text: redaction removes the underlying text data so it cannot be recovered by selecting, searching, or extracting.

Not all PDF editors support true redaction. Drawing a black box over text is not secure -- the text beneath is still in the file and can be extracted. If you need to redact sensitive information, verify that your tool performs actual content removal, not just visual overlay.

Rearranging Pages

Reordering pages is an editing operation that goes beyond individual page modifications. If you need to move pages around within a document, the PDF page organizer is a better fit than the annotation editor. This pairs well with page extraction if you need to remove pages entirely. See our guide on how to merge and split PDFs for detailed page manipulation workflows.

Cropping Pages

Cropping changes the visible area of a PDF page. This is useful for removing white space, margins, or unwanted border content. Cropping in PDF does not delete the hidden content (it just changes the crop box), but it affects how the page displays and prints.

Editing Scanned PDFs

Scanned PDFs present a unique challenge: the "text" is actually an image. You cannot select, highlight, or edit text that is really just a photograph of text. To edit a scanned PDF:

1. Run OCR first. Optical Character Recognition converts the scanned image to selectable, searchable text. See our guide on how to OCR scanned documents.
2. Edit the OCR-processed PDF. After OCR, the text layer is real text that can be selected, searched, and annotated normally.
3. Add new content. Text boxes, images, signatures, and annotations work on scanned PDFs just as they do on native PDFs.

Without OCR, your editing options on scanned PDFs are limited to adding content on top of the scanned image. You can still add text boxes, images, signatures, and shape annotations -- you just cannot interact with the underlying scanned content.

PDF Editing Across Devices

Desktop

Desktop PDF editors offer the most complete feature sets. Adobe Acrobat Pro is the industry standard but requires a subscription. Free alternatives include:

• The online PDF editor on ConvertIntoMP4 (browser-based, no install)
• Preview on macOS (basic annotations and signatures)
• LibreOffice Draw (open-source, full editing)
• Foxit Reader (free annotations, paid full editing)

Mobile

Mobile PDF editing has improved significantly. Both iOS and Android offer markup tools:

• iOS: Open a PDF in Files or Books app, tap the markup icon
• Android: Google Drive's built-in viewer supports basic annotations

For more capable mobile editing, the browser-based PDF editor works on tablets and smartphones with touch support for drawing and positioning.

Browser-Based

Browser-based editors require no installation and work on any device with a modern browser. They process files either locally (in the browser using JavaScript) or on the server. Server-side processing typically offers more features and handles larger files, while client-side processing is faster for small documents.

Saving and Sharing Edited PDFs

After editing, you have several options for the output:

Save with annotations intact. The annotations remain as separate layers that can be modified or removed later. Recipients can interact with comments, expand sticky notes, and respond to feedback.

Flatten the PDF. This merges all annotations, form data, signatures, and added content into the page permanently. Nothing can be edited or removed after flattening. This is the right choice when you want the edits to be permanent and tamper-proof. For details on flattening, see our guide on how to flatten a PDF.

Export to another format. Convert the edited PDF to DOCX for further editing in a word processor, or to images for embedding in presentations and web pages.

Wrapping Up

Online PDF editing bridges the gap between the rigid permanence of PDF and the need to modify documents after they are created. For adding text, images, annotations, signatures, and form data, browser-based editors provide a fast, accessible solution that requires no software installation or subscription.

The key is matching your editing needs to the right tool. Small modifications -- adding a date, signing a form, highlighting text, inserting a logo -- are perfectly suited for online PDF editors like the PDF editor. Substantial content changes -- rewriting paragraphs, restructuring sections, changing layouts -- call for converting to DOCX, editing in a word processor, and converting back to PDF.

Start with the edit you need, choose the tool that matches, and keep both the original and edited versions until you are certain the changes are final.