Dealing with PDF is a demanding job. And unfortunately, expecting ANY software to be able to automatically convert a PDF and do a perfect job is simply asking for a lot of trouble. If you search on Google for PDF and translation, you'll find thousands of pages describing all the same problem: it does not work. The only reasonable way to deal with PDF is using a decent OCR software to manually convert the PDF controlling the whole process and deciding (again: manually), what is text or what is table or picture and how the text has to be placed on the page. Next to that you need to open the converted file and correct remaining formatting issues to make sure the translation process will not end with double the page number of the source... Or you have someone doing this preparation for you. Relying on Studio (any other CAT) is not the proper way, even though the CAT vendors promise wonder.

I see. I thoght it would be easier than this, since there are many videos around, where they show I just click here and there and I can start working on my converted PDF file. Thank you for your answer.

Indeed, Google provides "solutions". But if you search forums for translators, you should notice this being the most often discussed translation topic and the answers are always the same.

PDF has been designed as a non-editable format.