Can I add more slides on my own to the presentation that I purchase? Can I duplicate any of the slides?

Yes, of course. You can add as many slides as you need and duplicate any of the three Masters.

How to Add Slides to a PowerPoint Presentation

To add a slide, locate the New Slide button on Slides area on the Home tab.

Notice that the New Slide button has two parts:

• the top, an icon of a slide,
• and the bottom, the New Slide text with an arrow.

Clicking on the top (icon) is a shortcut to adding a slide with the title and text layout.

Clicking on the bottom (New Slide text with the arrow) lets you choose exactly which layout you would like to use.

Please, follow this link for more information.

Please, follow this link to learn how to set one of the slides as a background.

How to Add Slides to a Keynote Presentation

Keynote creates a single Title slide when you first create a project. To add more slides, use a methods described below:

• Click the New button on the Keynote toolbar.
• Choose New Slide from the Slide menu.
• Press Command+Shift+N.
• Right-click (or Control-click) in the Slides list and choose New Slide from the menu.

If you need a slide that’s very similar to an existing slide then right-click the existing slide and choose Duplicate to create a new slide just like it.

Keynote adds the new slide to your Slides list and automatically switches to the new slide in the Layout pane.

Please, follow this link for more information.