You can save your iOS device transactions as well as details of your sales as a PDF file.

Save transaction details as PDF:

'Accounts' > 'Select Account' >'Open transaction details' > Select the upload icon and PDF in the toolbar. Then enter the location where you want the PDF saved (iClound, Drive, iBooks, Dropbox,...)

Save several transactions details as PDF: 

'Accounts' > 'Select Account' > 'Select Edit above the transaction list' > 'Select the desired transactions in the list of transactions' > Select the upload icon and PDF in the toolbar. Then enter the location where you want the PDF saved (iClound, Drive, iBooks, Dropbox,...)

Save all transactions of an account as PDF:

'Accounts' > 'Select Account' > 'Select Edit above the transaction list' > Select the upload icon and PDF in the toolbar. Then enter the location where you want the PDF saved(iClound, Drive, iBooks, Dropbox,...)