It's a good implementation, however you need to improve it.

It's a good implementation, however you need to improve it. You cannot write stuffs like count($this->pdo->query($this->queryString)->fetchAll(PDO::FETCH_OBJ));
You can't possibly return the entire dataset in an array and the count the elements of the array.
Make a select count(*) instead and return an integer.

Pagination is supposed to make your front end cleaner but also take weight from the database queries.

Thank you for the feedback. I believe your query scalar approach is better. I will refactor accordingly.