Adobe Acrobat Replacement for MacBook Air

Not sure what you mean that Adobe Acrobat is going away.

They are eliminating the perpetual license and charging monthly with a subscription model license.

If you think it is overpriced for what it is, then you are correct about that.

I use PDF Expert by Readdle Ltd., a Ukraine company.

Their customer service is very good.

It is a fraction of the price of Adobe Acrobat Pro.

It does not handle dynamic documents though where you can expand the number of fields in which you add inputs. They have a conversion process you or they can go through to deal with it and field entries. I find I still have to use Acobat reader to fill in documents. I still find Acrobat Reader does not allow you to save certain documents for which you just input the fields, which is its worst offense and why I hate it.

Just save the pdf then open it with preview; right click and open with (you can change this to default app later if you find Preview useful). Once Preview has opened the pdf then in the toolbar at the top there's a small pencil in a circle. Click it and the markup bar drops down. You can play with the icons to work out what they do - there's select, magic select, line drawing, shape drawing adding text and setting the colours and sized of lines and text.

To save as in any Apple menu click File in the menu bar then press and hold the option key and Save should turn into Save As.

It depends what you use it for. If you just read and convert pdfs to jpeg with the odd bit of markup editing and combining docs then Preview is OK. If you need more pro-type or business use then someone might be along soon with advice or I'm sure an internet search will bring up a whole host of potentials.

To open with preview:

If you have a mouse with a right button, you right click on the file name to see the menu options.

Mouse over to select the "Open With" menu option and that should bring up the apps that can be used to open a .pdf file.

If you have no mouse with a right click button ( MacBook air with touch pad):

Select the "Control" button on the keyboard and then click the mouse on the file name to see the menu options.

Using the touch pad, move the cursor (finger) to select the "Open With" menu option and select the app you want to use to open it.