The researchers are doing this study to find out whether using the chemotherapy regimen NALIRIFOX in combination with ablative dose radiation therapy (AD-XRT) and the standard chemotherapy drug capecitabine is an effective treatment approach for people with locally advanced or borderline resectable pancreatic ductal adenocarcinoma (PDAC) before surgery. This type of treatment approach is called total neoadjuvant therapy (TNT). The researchers will also look at whether the sequence of the treatment approach (NALIRIFOX + ADXRT and capecitabine followed by surgery, when it is possible) is effective and causes few or mild side effects in participants. An important purpose of the study is to see how the study treatment (NALIRIFOX + AD-XRT and capecitabine) affects participants' quality of life. The researchers will measure quality of life by having participants fill out questionnaires