Yes, you can by going to change by going to the Settings page, under Default Settings click on Edit:

Under Button Text you can change the text to the one that you prefer and click on Save:

If you wish to only change the label of the Pre-Order button on certain pre-order product only, please go to Products and click on the "Edit Settings" button:

You can change the text under the respective functionality's Button Text:

Did this answer your question?