Method 1
Step 1: Click the button Add PDF File as marked by the red rectangle as follows:
Step 2: Choose a PDF file , and then click the button Open.
If you want to convert more PDF files, please repeat step 1 and 2;
if not, go to step 3.
Step 3: Chose the file, and then click the button Convert.
step 4: Name the new file in the added box and click the button Save.
Method 2
Step 1: Drag a PDF file to the list box.
Step 2: Repeat step 3 and 4 in the first method.