Step 1: Count the digits used for pages 1 to 9.
Each of these pages uses 1 digit, so for 9 pages, the total number of digits is:
\[
9 \times 1 = 9 \text{ digits}.
\]
Step 2: Count the digits used for pages 10 to 99.
Each of these pages uses 2 digits, and there are \( 99 - 10 + 1 = 90 \) pages in this range.
Thus, the total number of digits is:
\[
90 \times 2 = 180 \text{ digits}.
\]
Step 3: Count the digits used for pages 100 to 366.
Each of these pages uses 3 digits, and there are \( 366 - 100 + 1 = 267 \) pages in this range.
Thus, the total number of digits is:
\[
267 \times 3 = 801 \text{ digits}.
\]
Step 4: Total number of digits.
The total number of digits is:
\[
9 + 180 + 801 = 990 \text{ digits}.
\]