I've never understood why copying text from digitally native PDFs (created directly from digital source files, rather than by OCR-ing scanned images) is so often such a poor experience. Even PDFs produced from LaTex often contain undesirable ligatures in the copied text like fi and fl. Text copied from some Springer journals sometimes lacks space between words or introduces unwanted space between letters in a word ... Is it due to something inherent in PDF technology?
However, I don't know if XPS handles the copying of text better.