Reading files

I am having trouble reading a document as certain headings and titles are now blurred. Never used to be like this and I have deleted and reinstalled the file and it makes no difference. I am finding that another file today looked like it had been redacted with black shading blocking diagrams and words . Does anyone know what I can do about this ? If I go to Adobe via safari then the document is fine to read and no problems . I can't do this on a regular basis as I need to access the files quickly while I'm on a job and don't always have signal to get on to internet. My work is mobile and never in same place so I don't have access to computers or laptops . I am currently using iphone 11 pro