Page number in PowerPoint slide not appearing

The macro recorder is not available in Microsoft Office PowerPoint 2007. Instead, you can use Visual Basic for Applications (VBA) to create or edit macros. To create or edit a macro by using VBA, do the following:

1. On the Developer tab, in the Code group, click Macros.
2. In the Macro dialog box, in the Macro name box, type a name for the macro.
3. In the Macro in list, click the template or the presentation that you want to store the macro in.
4. In the Description box, type a description for the macro.
5. Click Create to open Visual Basic for Applications.

Source: MS Powerpoint 2007 Help File

Why was the record macro feature removed from Powerpoint 2007?

According to Steve Rindsberg, PPT MVP, macro recorder wasn't all that great even in 2002/2003. It missed all animation stuff and other things. With all the changes to the object model in 2007, bringing the recorder up to speed would've taken a LOT of work. They probably decided the resources would be better spent on other features and rather than deal with a lot of tech support problems with the macro recorder, and they removed it. (Tech-archive)

If you're looking for an option or configuration setting that will just automatically add it to every presentation you create, there isn't one. However, if you edit the Header or Footer, you can automatically add slide numbers there and have them appear on all slides.

http://office.microsoft.com/en-us/powerpoint/HA101181931033.aspx