1. One-digit page numbers (1 to 9):

• Number of pages: 9
• Digits per page: 1
• Total digits: $9 \times 1 = 9$

2. Two-digit page numbers (10 to 99):

• Number of pages: 90 (99 - 10 + 1)
• Digits per page: 2
• Total digits: $90 \times 2 = 180$

3. Three-digit page numbers (100 to 150):

• Number of pages: 51 (150 - 100 + 1)
• Digits per page: 3
• Total digits: $51 \times 3 = 153$

Total digits used:

• 9 (one-digit) + 180 (two-digit) + 153 (three-digit) = 342

Therefore, the total number of digits printed is 342.