PDF Annotator
Add your PDF file, choose any options you need, and DOC321 prepares the PDF result for you.
Annotate a PDF
Highlight passages, add text notes, and draw boxes directly on PDF pages.
Choose a PDF file to begin.
Everything you need
Why use PDF Annotator?
The working tool stays at the top of the page. These details explain what it does well and what to expect before you process an important file.
Highlight important passages
Drag directly over a region of the preview to add a translucent highlight annotation-style overlay.
Add text notes and boxes
Place short text notes with a click or drag a blue box around areas that need attention.
Undo before export
All changes are queued first, so you can undo or clear them before creating the annotated PDF.
Simple from start to finish
How to use PDF Annotator
Every tool keeps the main job obvious: add what you have, make the needed choice, run the task, and leave with a usable result.
01
Add PDF
Choose the file or content you want to work with in the hero workspace, or drag it into the upload area.
02
Choose your options
Set only what is necessary for the result you want.
03
Run PDF Annotator
Annotate and mark up a PDF online
04
Use PDF
Review the result, download it, or continue into a closely related workflow.
Annotate and mark up a PDF online
Annotate PDF pages in your browser with highlights, text notes, and boxes, then export a separate marked-up PDF.
Know what goes in and comes out
Clear input and output expectations make it easier to choose the right tool before you begin.
PDF inputPDF output
A simpler way to finish the job
About PDF Annotator
PDF Annotator is built around one clear outcome: annotate and mark up a PDF online. If you already have PDF and need PDF, this page keeps the working tool, the explanation, and the useful next steps together. You do not have to dig through a large software menu just to find the feature you came for. Start with the workspace above, complete the task, review the result, and continue only if your document actually needs another step. If the file needs preparation first, Compress PDF may be a useful companion because it helps you reduce PDF file size.
When PDF Annotator is useful
PDF Annotator focuses on one document job instead of surrounding it with unrelated controls. That matters when the task is small but necessary and you want to finish it quickly. Bring in the supported file or content, choose the settings that affect your result, run the task, and review what changed before you download it. The page is structured so the main action remains clear from the moment you arrive.
Typical uses include preparing PDFs for email, forms, school or office submissions, document archives, client handoffs, printing, and workflows where a PDF needs to be edited, organized, converted, reduced, protected, or made easier to share. For another common route in the same workflow, Edit PDF can help you edit a PDF online without leaving DOC321.
Prepare the source for a better result
For PDF files, start with the cleanest source you have. Password protection, damaged files, unusual embedded fonts, very large scans, or image-only pages can affect what any browser-based PDF workflow can read or change. If the document is a scan and you need selectable text, OCR may be the better first step. If exact page appearance matters, review every important page after processing before you send, print, archive, or upload the result.
Before you process anything important, make sure you selected the correct version of the source file. Check the file name, page count, visible content, and whether the document opens normally. If the source is protected, damaged, scanned, or simply the wrong format, fixing that first usually saves time. A tool such as Merge PDF can be the better first step when you need to combine multiple PDF files into one PDF.
Review the output before you rely on it
Browser tools can make document work much faster, but the final review still matters. After processing, check the parts of the file that affect your real task: page order, text, images, spacing, file size, formulas, slide layout, links, or whatever else is important for the document type. If you are sending the result to a school, employer, customer, government service, printer, or another application, confirm that the file opens correctly and contains the expected information before you submit it.
That quick check is especially useful when a document contains unusual formatting or was originally created in another application. The goal is not just to produce a download; it is to produce a result you can actually use. If the result needs one more adjustment, Protect PDF is available to help you add password protection to a PDF.
Continue the workflow without starting over
Document work rarely ends with one action. After you annotate and mark up a PDF online, you may need to make the file smaller, convert it again, combine it with another document, extract text, edit content, protect it, or prepare it for sharing. DOC321 keeps related tools connected so the next step is easy to find without returning to a search engine or opening a different service.
For example, Split PDF helps you split or extract pages from a PDF. You can also use Unlock PDF when the next job is to remove PDF password encryption with a known password. If neither matches what you need, browse the PDF tools section for tools from the same document family, or open the complete tools directory to see every live DOC321 workflow on one page.
Designed for quick, private document work
DOC321 is designed around practical browser tasks rather than account creation, advertising, or unnecessary setup. The most important action stays near the top of the page, while supporting information sits below it for people who want to understand the workflow in more detail. That means a first-time visitor can begin immediately, while someone handling a more important document can read the guidance, check supported inputs and outputs, compare related tools, and review common questions before processing anything.
The same page structure is used across PDF, Word, image, spreadsheet, presentation, text, and document-creation tools so the site feels familiar after the first visit. Individual tools still keep their own color and workflow, but the interaction pattern stays predictable: understand the task, work in the hero, see the result, and move to the next relevant step only when you need it. This consistency is meant to reduce mistakes and make repeated document work faster over time.
PDF Annotator FAQs
Answers to common questions before you start.
Can I annotate a PDF online?
Yes. Open the PDF, choose a markup tool, add highlights, text notes, or boxes, then export the annotated copy.
Are these native PDF comments?
No. This version applies visible markup directly to the PDF page rather than creating separate comment objects.
Can I annotate more than one page?
Yes. Navigate between pages and keep adding markup before exporting the final PDF.
Get the rest of your document work done here.
When this task is finished, DOC321 has the next PDF, Word, image, spreadsheet, presentation, or writing tool ready.