Hi @Anonymous,
what’s the data source the app based on?
Do you want to get all items from the data source the send them in an email at a time?
If you want your flow to be triggered by clicking the button on PowerApps, then you could use the trigger PowerApps Button. After that, let’s say your app is based on SharePoint list, add an action Get rows to get all the data from the list. If you would like to send all the items at a time, add the action Create HTML table or Create CSV table. Then send an email with output from the HTML/CSV table.

Besides, if you want to email a PDF file, please try to use the action create file and format it as .pdf file. then send an email with the file created previously.
Hope it could be your reference. Please feel free post back if you need more help.
Best regards,
Mabel