Your pachysandra has two problems:
The little specks on the lower leaf surfaces is euonymus scale, a sucking insect. For information on handling this pest, put 'euonymus scale' into our website's search box.
The circular spots on the leaves are from a fungal disease known as volutella. Put this in the search box also. Select the groundcover information. Follow all the steps to eradicate it, which will include removing built-up debris in the bed, mowing it down and raking it out in the spring (the roots are very vigorous and will put out new growth), and avoiding overhead watering and autumn leaf coverage.