Use the "Filter" button on the "Account transactions" page to filter your transactions. Then click the "Export" button.
All receipts attached to the selected transactions will be downloaded collectively in the original format (e.g. PDF, JPEG) in a folder. A CSV file will also be downloaded.
Each document has an assigned number at the beginning of the file name. You can also find this number in the "Index" column in the CSV file. This way you can easily assign each document to the appropriate transaction.