Step 1: Expand the integrand.
\[
\int \sec x (\sec x + \tan x) dx = \int \sec^2 x \, dx + \int \sec x \tan x \, dx
\]
Step 2: Recall standard integrals.
\[
\int \sec^2 x \, dx = \tan x + C
\]
\[
\int \sec x \tan x \, dx = \sec x + C
\]
Step 3: Combine results.
\[
\int \sec x (\sec x + \tan x) dx = \tan x + \sec x + C
\]
Final Answer: \[ \boxed{\tan x + \sec x + C} \]