No there is no spell checking available in PD.
You write that there is a lot of text. What I do it such case is, inserting the text using a word processor with a spell checker on board. I separate text in paragraphs and lines and cut and paste the texts into the PD title and subtitle rooms. It goes a bit faster too. The disadvantage of working ahead is that you need to have a clear text plan. You can of course keep the word processor and PD side by side.
Having a spell checker available in PD would in some cases be very useful. You can submit a suggestion in the file/Rate us & provide suggestions menu.
I’d rather have the developers work on (more) stability and improving usability