PDF Merge X: Merge PDF

I'm sorry to hear that you feel tricked. The reason this app is free is to offer users the possibility to see if the feature set is what they are looking for. I tried to make people aware of it by stating this right at the beginning of the app store description page.

Hi There! If you want to move documents you can do this directly inside PDF Modify or with the Files app. With PDF Modify 3 you no longer have to import any PDFs to the app. You can open and edit them from anywhere (directly from PDF Modify, the Files app, or any other app which is able to share PDFs). For a preview of the document you can do a long press on the file thumbnail and then select "Preview" in the context menu. Or alternatively press "Select" and then choose the document. In an upcoming update I will add a dedicated Preview button in the edit view to make things easier. Should you have any further issues or feedback, please share them with support@sasystems.ch, I am interested to hear them. Thanks for using the app.

Hi There! Version 3.1 just got released with a new Preview button inside the edit view. This will hopefully improve everybody's workflow. If you like this new feature I would be very grateful if you could update your review. Thank you very much. Alternatively you can do a long press on the file thumbnail in the overview view and then select "Preview" in the context menu. Or select Edit in the overview, then selecting a document and press Preview from the top-right.