I have only attended Computer Based Exams in ACCA and this is my fisrt paper based exam (professional level) and I am not sure what type of pen I have to use.
Hi, I was facing the same issues in the previous September attempt as it was my first PBE.
We are allowed to only use BLACK BALLPOINT PENS. This means you are not allowed to use gel pens or ink pens and only the color black can be used (Blue is not allowed). You are not allowed to use a pencil. You have to write within the margins and it is better to start a new question on a new page. Leave good spaces and try to write readable words.
Also there is a facebook page called ACCA x USM. They post good tips for exams regarding everything. Do follow them.