What you can actually change in a PDF
A PDF is designed to look the same on every computer, which is why it locks down most editing. You cannot straightforward open a PDF in the same way you open a Word document and start retyping. But you can change specific things: text in fillable forms, annotations (notes and highlights), the order of pages, or the entire content if you use the right tool.
The type of PDF matters. A fillable PDF has form fields built in — boxes where you type information. A scanned PDF is a photograph of a document, so the text is not actually text; it is an image. A standard PDF has text and images but no form fields. Each type requires a different approach.
Before you start, decide what you actually need to change. If you only need to fill in blanks on a form, you may not need to buy anything. If you need to rewrite paragraphs or move pages around, you will need a dedicated tool.
Key Takeaways
- Fillable PDFs with form fields can be edited in free tools like Adobe Reader or Preview (Mac), but only in the boxes that were set up for input.
- Scanned PDFs are images, not text, so you cannot edit them without optical character recognition (OCR) software that converts the image to readable text first.
- To rewrite paragraphs, delete pages, or move content around, you need a paid PDF editor like Adobe Acrobat Pro or an alternative like PDFtk or LibreOffice.
- Free online PDF editors work for straightforward tasks but upload your file to someone else's server, so avoid them for sensitive documents.
Editing fillable forms without paying
Adobe Reader (the free version) lets you fill in form fields on any PDF that was created with fillable boxes. Open the PDF, click in a box, and type. You can save the filled version to your computer. This works on Windows and Mac.
On a Mac, Preview (built into the system) also fills forms. Open the PDF, click Tools in the menu, then Annotate, then Text. Click where you want to type. Preview also lets you highlight, underline, and add notes in the margins.
The catch: you can only fill in the boxes that were created as form fields. If the PDF was made from a scanned document or a document without form fields, these tools will not let you type in the blank spaces. You will see that the text boxes do not respond to clicking.
Converting a scanned PDF so you can edit the text
A scanned PDF looks like a document but is actually a photograph. The words are not selectable text — they are pixels. To edit the actual words, you need optical character recognition (OCR), which reads the image and converts it to editable text.
Adobe Acrobat Pro includes OCR. Open the scanned PDF, go to Tools, then Recognize Text, then In This File. Acrobat reads the image and converts it to searchable, editable text. This usually takes a few seconds to a few minutes depending on the file size.
Free alternatives: Google Drive can perform basic OCR. Upload the scanned PDF to Google Drive, right-click it, select Open With, then Google Docs. Google converts the image to a document you can edit. You can then read it as a PDF or Word file. The quality depends on how clear the original scan is.
After OCR converts the text, you can edit it like any other document. Keep in mind that OCR is not perfect — handwriting and poor-quality scans often produce errors that you will need to fix by hand.
Rewriting, deleting, or rearranging pages
Adobe Acrobat Pro is the standard tool for heavy editing. It lets you select and delete text, rewrite paragraphs, delete entire pages, rearrange pages by dragging them, and add new pages. The monthly subscription is around $15 to $20, depending on your region and whether you bundle it with other Adobe products.
PDFtk is free and runs from the command line (text-based interface), so it is not for beginners. It excels at splitting PDFs, merging them, rotating pages, and removing pages. If you work with PDFs regularly and are comfortable with technical tools, it saves money.
LibreOffice Draw is free and works on Windows, Mac, and Linux. Open a PDF in Draw, and you can edit text, move objects around, and delete content. The editing is less polished than Acrobat, but it handles most tasks. You can save the result as a PDF or convert it to another format.
Paid alternatives to Acrobat: PDFpen (Mac only, around $80 one-time), Nitro Pro (Windows, around $150 one-time), and Sejda (web-based, free tier with limits, paid plans start around $10 per month). Each has different strengths — Sejda is easiest for beginners, PDFpen is fastest on Mac, Nitro Pro handles large batches of files well.
Adding signatures, notes, and highlights without changing the original text
You do not need a full editor to sign a PDF or add comments. Adobe Reader (free) lets you add a signature, highlight text, underline, and add sticky notes. Open the PDF, click the Comment button (speech bubble icon), and choose your tool. Your annotations stay with the file when you save it.
On Mac, Preview has the same features under Tools > Annotate. You can sign with your trackpad or mouse, add text boxes, and draw shapes.
DocuSign and HelloSign (now Dropbox Sign) are designed specifically for signing documents. You upload a PDF, add signature fields, and send it to others to sign. Both have free tiers for a limited number of documents per month. These are useful if you need a legal record of who signed and when.
Avoiding free online PDF editors for sensitive documents
Many websites offer free PDF editing — you upload your file, make changes in your browser, and read the result. Tools like Smallpdf, ILovePDF, and PDF.io work this way. They are convenient for one-off tasks, but they upload your file to someone else's server.
If the PDF contains personal information (tax returns, medical records, financial statements, legal documents), uploading it to a third-party server creates a privacy risk. The company may store the file temporarily or permanently, and a data breach could expose your information. For sensitive documents, use a tool that runs on your own computer: Adobe Reader, Preview, LibreOffice, or Acrobat Pro.
If you do use an online tool, check the privacy policy. Some delete files when ready after read; others keep them for days or weeks. Read the terms before uploading anything you would not want to lose or have seen by others.
Choosing the right tool for your situation
| What you need to do | Best free option | Best paid option |
|---|---|---|
| Fill in form fields | Adobe Reader or Preview | Not needed |
| Sign a document | Adobe Reader or Preview | Dropbox Sign or DocuSign |
| Edit a scanned PDF | Google Drive (OCR) | Adobe Acrobat Pro |
| Rewrite text or delete pages | LibreOffice Draw | Adobe Acrobat Pro |
| Split, merge, or rotate pages | PDFtk (command line) | Adobe Acrobat Pro |
| Add highlights and notes | Adobe Reader or Preview | Not needed |
Start with what you already have. If you own a Mac, Preview handles most annotation and basic editing. If you use Windows and only need to fill forms or sign, Adobe Reader is enough. Only pay for a tool if the free options do not do what you need.
Frequently Asked Questions
Can I edit a PDF that is password-protected?
If the PDF is locked with an owner password (which prevents editing), you cannot remove that protection without the password. If it is locked with a user password (which prevents opening), you need the password to open it at all. Some older PDFs have weak encryption that specialized tools can bypass, but this is not reliable and may violate the document owner's intent.
What happens to the file size when I edit a PDF?
Editing usually increases file size slightly because the tool adds layers of information about your changes. If you delete pages or compress images, the file may shrink. If you are sending the file to someone else and size matters, check the file size before and after editing.
If I edit a PDF in LibreOffice and save it, will it look the same on someone else's computer?
Usually yes, but LibreOffice sometimes reformats text slightly when saving to PDF. Test by opening the file on another computer before sending it to someone who needs it to look exact. Adobe Acrobat Pro is more reliable for preserving formatting across computers.
Can I undo changes after I save a PDF?
No. Once you save, the changes are permanent. Most PDF editors let you undo while the file is open, but closing and reopening the file means the undo history is gone. Save a backup copy of the original before you start editing.
Why can't I edit text in some PDFs even though they are not scanned?
The PDF may have been created with text as an image rather than selectable text, or it may have been intentionally locked by the creator. Try opening it in Adobe Acrobat Pro — if it still will not let you edit, the creator restricted editing permissions. You would need the owner password to remove that restriction.