if you want to do it offline, jus follow these steps

• Open a file in Acrobat.
• Click on the Edit PDF tool in the right pane.
• Click the text or image you wish to edit. Acrobat shows you the tools you’ll need.
• Add or edit text on the page. Lines and paragraphs reflow automatically, or you can click and drag to resize elements.
• Add, replace, move, or resize images on the page using selections from the Objects list.
• Click on the Link, Headers and Footers, Watermark, or Background tool to edit your PDF further.

but if u want to do it online, u can try https://www.pdfescape.com/