How to Edit a PDF Online: Add Text, Images, and Annotations
Learn how to edit PDF files online without expensive software. Covers adding text, images, annotations, highlights, comments, form filling, signature placement, and the limitations of PDF editing.
Emma Wilson·February 19, 2026·13 min read
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.
Editing a PDF document with online tools
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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.
Adjust the font, size, and color to match the surrounding content
Position the text precisely using drag-and-drop or arrow keys
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:
Capability
PDF Editor
Word Processor
Replace a word or phrase
Yes (limited)
Yes (full)
Rewrite entire paragraphs
Difficult
Easy
Add new paragraphs
Limited
Easy
Reflow text after changes
No
Automatic
Change fonts globally
No
One click
Restructure headings and sections
No
Easy
Update table of contents
No
Automatic
Track changes
No
Full support
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.
Pro Tip: When adding text that needs to match the existing document's font, use the eyedropper or font detection feature if available. If not, common document fonts are Times New Roman (12pt) for legal/formal documents, Arial (11pt) for business documents, and Calibri (11pt) for modern Microsoft Office documents. Getting the font and size right makes added text indistinguishable from the original.
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:
Upload your PDF
Select the Image tool
Upload the image file (JPG, PNG, or SVG)
Position the image on the page using drag-and-drop
Resize by dragging the corner handles
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.
Annotation Type
Best Used For
Persists When Printed?
Highlight
Marking important text passages
Yes (as colored background)
Underline
Emphasizing key terms
Yes
Strikethrough
Indicating proposed deletions
Yes
Sticky note
Adding comments and feedback
Icon prints, content may not
Text box
Adding visible notes on the page
Yes
Arrow/line
Pointing to specific areas
Yes
Rectangle/circle
Enclosing or grouping content
Yes
Freehand drawing
Circling, marking, sketching
Yes
Stamp
Adding "Approved", "Draft", etc.
Yes
Adding annotations and markup to a PDF document
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:
Open the PDF in the editor
Click on a form field
Type your response or select an option
Tab to the next field
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.
You are reviewing a document and need to provide feedback.
Upload the PDF
Use the Highlight tool to mark important passages
Add Sticky Notes with comments at specific points
Use Strikethrough to indicate text that should be removed
Use the Text Box tool to suggest replacement text
Draw arrows to connect related items
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.
Upload the PDF
Add the logo image to the first page
Position and size it appropriately (typically top-right or top-left corner)
Apply the logo as a watermark to all pages if the tool supports it
Download the branded document
Pro Tip: When reviewing a PDF with annotations, use different highlight colors to categorize your feedback. For example: yellow for "needs clarification," green for "approved as-is," pink for "needs revision," and blue for "reference for later." This color-coding system makes it faster for the document author to prioritize and address your feedback.
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.
Before and after editing a PDF with text and image additions
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:
Run OCR first. Optical Character Recognition converts the scanned image to selectable, searchable text. See our guide on how to OCR scanned documents.
Edit the OCR-processed PDF. After OCR, the text layer is real text that can be selected, searched, and annotated normally.
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.
Save Option
Annotations Editable?
File Size
Best For
Save with annotations
Yes
Slightly larger
Ongoing review process
Flatten
No (permanent)
Slightly smaller
Final distribution
Export to DOCX
Converted to Word formatting
Varies
Further editing in Word
Export to images
Rendered into pixels
Varies
Presentations, web use
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.
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About the Author
Emma Wilson
Digital media specialist with expertise in audio engineering, podcast production, and ebook publishing workflows.
