Windows Products and .pdf files

Hello. I look after the web site Harcove.com. It uses your homestead system. One problem I do have is that once a month I post our Strata/Homeowner Council minutes to their meeting. It is provided in a .pdf file and I simply upload using file manager and put it into a 2015 file using the date of the meeting. I then go on the site a put a monthly link to the file. I then send out an email to the owners saying the minutes are on the website. All has worked well until recently.
I am getting owner saying they cannot read the minutes. In each case they are owners using apple products. They can open the file using windows but cannot open the file using apple.
What and I doing wrong. I need your help please.