Reading device and control method with notification of an error or improvement associated with document transport and data transfer speed

A reading device connected to an external device, the reading device comprising:

• a transport section configured to transport a document;
• a reading section configured to read the document transported by the transport section;
• a data generation section configured to generate image data of the document read by the reading section;
• a transfer section configured to transfer the image data to the external device;
• a notification section configured to notify information to a user;
• and
• a control section, wherein
• the control section is configured to
• control a transport speed of the document by the transport section based on a transfer speed of the image data by the transfer section and
• when the transport speed is changed, cause the notification section to notify using a change notification indicating a change in the transport speed, wherein
• when the transfer speed is less than an improvement threshold value, the control section causes the notification section to notify using an improvement notification prompting improvement of the transfer speed, and
• when the transfer speed is less than an error threshold value, which is smaller than the improvement threshold value, the control section stops the transport section and causes the notification section to notify of an error.