You can check the user guide here: https://www.acethinker.com/pdf-converter/howto-use-pdf-converter-pro.html
Hit on the account icon located in the upper right area of AceThinker PDF Converter Pro's interface. Switch to the Sign Up box by clicking the 'Sign Up' option from the' Login' box. You will be asked to state a valid email and a password and get your verification code to get your verification number.
To protect PDF files with a password, you have to save your document into PDF by clicking the ‘Save As’ button. After that, click the ‘Options…’ button and tick the ‘Encrypt the document with a password. You can also use AceThinker Converter Pro, drag the file into the ‘Protect PDF’ box of the tool’s interface and enter your preferred password.
Convert PDF to Word using AceThinker PDF Converter Pro by logging in to your account and clicking the ‘Convert PDF’ box option. Select the PDF file you want to convert and open it. Once opened, click the ‘Convert’ blue button on the lower right side of the interface, and the PDF file will be converted to a Word document.
Open the PDF file from the 'Split PDF' box option from AceThinker PDF Converter's interface. The tool will then provide options such as 'Extract every page into a PDF' or 'Select pages to extract.' Input a specific range of pages according to your preference and convert it.
Log in to your account to AceThinker PDF Converter Pro and tap on the ‘Merge PDF’ box option. You can now select all PDF documents you want to download and convert them. Once the conversion is finished, you can open the merged file.
To extract images from PDF, log in to AceThinker Converter Pro. Click the ‘Extract Images from PDF’ and open the PDF document you want to acquire images from. You can now tap on the ‘Convert’ button and open the folder to see extracted images.