How do I convert a word document to a pdf without losing it’s formatting on iPad?

Consider that Word is a Microsoft product - not Apple. If you are using the Microsoft Word or Office App on your iPad, your ability to export documents to different formats will be determined by the respective Microsoft App's capabilities. If you need assistance with MS Apps, you would be best advised to seek assistance from Microsoft's own technical support resources.

Microsoft aside, most MS Word documents can be opened and edited on your iPad using the Apple Pages App - which will import the Word document and, insofar as is possible, will preserve the source document format. From here you can export the Word document to other formats - including PDF.

Having opened the Word document in Pages, Print and Export are accessed from the associated Document menu.