PDF Background Color

[defaultw49eohq3cb0x]

My friend A is helping me with a PDF related matter using Adobe Acrobat Reader DC (32-bit). 

I sent A a .pdf  with a white background that I would like changed to black. A managed to do so (kudos to Adobe Acrobat Reader DC for this handy feature). A saved the file, confirmed that it is a black background, and sent it my way via email and Telegram. On both mediums (and on my PDF reader), it reappears as having a white background. 

Why is that? How do I get it to appear in a black background if I no longer have Adobe Acrobat and all other alternatives I have attempted failed? I tried opening the files on a x64 PC and on iOS - if that matters in the slightest. 

P.S.: If you are going to suggest I renew Adobe Acrobat / repurchase a license, don't. It is not helpful advice. 

[Thom Parker]

What exact steps did you take to convert the background to black? And can you post the PDF with the converted background, or create a sample using the same technique and post that?

In general, it is not possible to make permenant changes to PDF page content with Reader. Acrobat Pro is required for this. 

[defaultw49eohq3cb0x]

@Thom Parker I am not able to post the converted PDF here because I am unable to replicate without Adobe Acrobat. 

@Bernd Alheit yes I did use Accessibility to change the background color. 

@Test Screen Name it doesn't explain how on A's end, the saved PDF opens with a black background when it was originally white (which sounds like the file was changed), and why it would not carry over via email. 

[Test Screen Name]

I can tell you Reader cannot change a background. That is definite. I believe A changed the background colour and sees that. There's not really any more to say. If A is trying to convince you they know a trick to edit AND change the background IN READER, then A is tricking you; or tricking THEMSELVES (many people honestly believe that the Accessibility Settings change files permanently and get in all sorts of difficulty).

[Bernd Alheit]

Have you changed the preferences at Accessibility.

[Test Screen Name]

I think A changed their own display preferences. They changed only how A sees it. The file doesn't change. Sounds normal. A doesn't have a useful trick.