To edit pdf on Mac Pro

Adobe Acrobat Reader DC has a free version

see: Top 10 Free PDF Editors for Mac 2019 - Updated

I can say PDFpen is one of the best pieces of software I ever purchased many years ago.

PDFexpert is another.

Apples built-in Preview.app has some capabilities, but not a true PDF editor that many demand:

How to edit images and mark up PDFs with Preview on your Mac

Hi,

Try to search at Mac App Store since you can't open Apps which download from Apple unauthorized sites.

Personally I always choose to downlaod straight from the developers site if I have the option—many AppStore apps are hobbled in some way to abide by all the hoop jumping. TextWrangler was a great example—

non the less the Apple approved way to open apps directly from a developer website is holding the Control key once downloaded..this has never been an issue.

On your Desktop/Downloads folder, locate the app you want to open.

Don’t use Launchpad to do this. Launchpad doesn’t allow you to access the shortcut menu.

Control-click the app icon, then choose Open from the shortcut menu.

Click Open.

The app is saved as an exception to your security settings, and you can open it in the future by double-clicking it just as you can any registered app.

Open a Mac app from an unidentified developer - Apple Support

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