Navigate to [https://docs.google.com/presentation/](https://docs.google.com/presentation/d/1uCVOaeNCiO3jcHEr8uNTm5SgQYDVToFfXO49pa42fyU/edit#slide=id.g2a24ac24970_0_0)
2
Click "File."
3
Click "Page setup."
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Select the size you'd like. If you want a custom size, click on "Custom."