Use a PDF editor like Adobe Acrobat, Foxit PDF Editor, or Nitro PDF
Open the PDF in the editor
Select the edit text or edit content tool
Click the text or image you want to change
Add, delete, or modify the content
Save the file as an editable PDF
If the PDF is scanned, run OCR first to convert it into editable text
Use a form tool to add fillable fields if you want users to type into the PDF
Export the file again after editing to keep the changes
If needed, convert the PDF to Word, edit it, and save it back as PDF