Adobe's Acrobat software allows you to read and make limited edits to documents stored in Adobe's popular Portable Document Format. PDF files are designed to appear identical no matter what system they're read on, but some users may have trouble reading documents in their original colours. Use Acrobat's Accessibility settings to make the text and background of the documents you read whatever colour you want, including darker or more contrasting colours than the original.
Open Acrobat's "Edit" menu, then click "Preferences."
Click "Accessibility" in the left pane to open the Accessibility Panel, which contains several options for making PDF documents easier to read for visually-impaired users.
Check the "Replace Document Colors" box to enable the colour-replacement settings. To make the document darker and easier to read, either click "Use High-Contrast colours" and select a colour combination from the drop-down menu, or click "Custom Color" and select a specific colour for both the text and background.
Click "OK" to close the Accessibility Panel and view documents with your new colours.