Your client seems to take a really long time to read even short texts. It may almost seem that they are dragging it out.
When they read something out loud they are hesitant and stumble over words. Sometimes they may even be so slow that they forget what the sentence is about by the time they get to the end.
One of the things that affects the speed of reading is dyslexia. Because individual letters and words take a long time to process, reading a long text is difficult. Sometimes a dyslexic person will have even trouble reading signs in the street unless they stop and concentrate.
Not all slow readers are dyslexic but most dyslexic readers are slow readers. This has a huge impact on their ability to access long texts such as policies and detailed instructions.
Another consequence of this reduced speed of processing is that many dyslexic readers find normal text very cramped and letters may even blend together for them. This is similar to somebody with slow reaction times driving very fast on a narrow road.
There are two things you should do to help a dyslexic person with reading: 1. Give them more time and be patient; and 2. Give them text that is formatted in an accessible way with lots of space and headings.
You can also help them by giving them the text in audio or have the computer read it out to them.