XLS
PDF files
XLS ( Excel spreadsheet) is an older file format used for storing spreadsheet data. Although largely replaced by XLSX, XLS files can still be opened and edited in Excel. They contain tabular data with formulas, charts, and formatting.
PDF (Portable Document Format), a format created by Adobe, ensures universal viewing with text,images, and formatting. Its portability, security features, and print fidelity make it pivotal in document tasks, apart from its creator's identity.