Even a short PowerPoint presentation can provide more information than your audience can comfortably absorb in one sitting. Citing references as footnotes helps them understand the information sources that went into your presentation. Adding a footnote isn't particularly complicated, and there are a couple of ways to do it.
Footnotes as Footers in PowerPoint
You usually use the Footer function to insert a footnote in PowerPoint. It works in much the same way as inserting headers and footers into other Office products, such as Word, and in non-Microsoft products as well, so it may feel familiar.
To start, click to place the cursor at the point in the text where you want to insert the number for your footnote. Type in the number and then repeat the process for any additional footnotes you want to add. Next, click Insert and then Header & Footer. Check the box labeled Footer. In the text box for the footer, insert the footnote number and the text that corresponds to that footnote.
Apply vs. Apply to All
Ordinarily, after you enter a footnote, you click Apply to finish adding a footnote to your slide.
Sometimes, though, you might want PowerPoint to add the same footnote to all slides. You wouldn't normally do that for citing a reference or a data source, but those aren't the only reasons for adding a footnote. You might want to include a legal disclaimer on each slide, for example, or copyright information for a trade name that is mentioned throughout.
In those cases, instead of clicking Apply, you click Apply to All. Usually, you also want to click the box immediately beneath the footer that says "Don't show on the title slide" unless you have a specific reason to display the footnote on the title slide as well.
Formatting the Number
Now that you've created the footnote, go back to where you placed the number that refers your readers to the footnote. Footnote symbols are customarily raised above the surrounding text to make them more visible, and it's good practice to follow that custom.
Highlight the number, then use the Font tab's pull-down arrow to open the Font dialog box. Click Superscript and then click Enter or OK.
Using a Text Box
Footers aren't the only way to insert a reference in PowerPoint. If you're already using the footers for information such as the date, your name and company or the title of your presentation, you can create a text box to hold a footnote instead.
Choose Format and then Drawing Tools from the ribbon bar, and then select the box tool. Draw a box at the bottom of the slide above the footer and type in the text. You can use the box's handles to resize it, if necessary, or adjust the font size for your text to make it fit.
Using Slide Master View
If you anticipate needing footnotes on most of your slides and want to avoid adding boxes manually, you can use the PowerPoint's Slide Master feature to add the text box once and have it appear on every slide. Choose View and then Slide Master, and insert the text box in a suitable place near the bottom of the master slide. When you're happy with its size and location, click either the Normal or Close Master View button.
You can use this technique with footers as well, instead of clicking Apply to All.
Endnotes in PowerPoint
If you don't need to cite your sources on a slide-by-slide basis, it is simpler to create endnotes instead. Simply number the footnotes in your text as you create your presentation and keep a running list of which references are cited in each footnote.
When your presentation reaches its final draft, and you won't be adding or removing sources any more, check your presentation one last time to verify that the footnotes are numbered correctly. Then turn your list of sources into a final slide or two in your deck, so your readers can find any specific citation they may want to research further.