Ответ:
1) These documents must be signed today.
2) This work could have been finished a week ago.
3) Dictionaries can not be used during the exam.
4) The application must be filled in with a pen.
5) The sick child should be examined by the doctor.
6) The photocopier may be used by anyone.
7) This story should not be told to little children.
8) Mobile phones must not be used during a flight in airplanes.
9) The dog should be taken to the vet.
10) The parcel could not have been delivered yesterday.