Go up to the View menu and select the menu item called ‘Show Annotations Toolbar. This will give you a toolbar along the bottom of your preview window to help you edit the pdf file.
Note: In Yosemite and El Capitan the ‘Annotations Toolbar’ has been Renamed to ‘Markup Toolbar’ so that it looks like this:
After you select the ‘View: Show Annotations Toolbar’ menu you will see a toolbar across the bottom of the preview window that looks like this:
These buttons will allow you to edit the pdf file. The left three buttons make an arrow, a circle or a rectangle. The fourth button along allows you to add text to the pdf.
If you click on the text box button – the 4th button across, you can then go up to your document and add in a text box like this:
This is a very easy way to fill in pdf files that are forms.
If you highlight the newly added text you can change the font by pressing Apple-T and the font window will appear.
You can’t delete what’s already in a document, but you can draw a rectangle over it to hide it and type something new over the top.
You’ll notice you can’t change the rectangle color from being black, but you can put a very fat white border around it so it looks like a white rectangle!
Please note, this is more of a hack than a proper way to edit. The original information that you have edited will still be there. It is just covered over. If someone deletes the box they will see the original document.
This is what led the the recent scandal in Australian Politics when all the private phone numbers of Australian politicians were accidentally leaked. The deleted the phone numbers from public documents by changing the colour from black to white. But they didn’t realise someone could still get the numbers out of the documents.
If you want to totally change the images and text on an existing pdf file you will need an application like Adobe Illustrator that can actually edit the content of pdf files. But if you only want to make small changes, the built in preview app will do the job!
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