Issues of PDF drawings

I am a mechanical engineer who relies heavily on PDF drawings for my work. I frequently use my iPad and iPhone to access these files. Typically, when I open a PDF drawing as an email attachment on my iPad, everything displays correctly. However, I encounter a peculiar issue when I open the same attachment on my iPhone: all the dimensions on my drawings appear with rectangles around them. 

Mechanical drawings often contain many dimensions, and seeing each one enclosed in a rectangular box makes the drawings cluttered and difficult to read. This issue also occurs when I open the same attachment in the Goodnotes application on my iPad .

I am curious if others have experienced a similar problem and would be happy to share some screenshots to illustrate what I am encountering. It is important for me to find a resolution, as accurate and clear PDF drawings are essential for my engineering work.

photo below is a snapshot of the drawing I’m talking about when I open it in goodnote or when I opened it directly from attachment of my email on iPhone and you can see all those rectangular around the numbers

drawing below is when I opened it directly from attachment of my email on my mini iPad