You can't scan a resume into Dilly
I only read text PDFs. If you printed your resume to PDF from Word, Google Docs, or Pages, that's a text PDF and I'm good. If you scanned a paper copy with a phone or printer, that's an image, and I can't pull the words out of an image. Re-export from the original file (or paste the text in) and I'll take it from there.
Try paste-as-text
If the PDF will not parse, copy the text and paste it into the resume import text box. Plain text always works.
Keep file size reasonable
Under 5MB is safe. Above that, compress or save as a smaller PDF first.
Avoid very columnar templates
Two-column resumes can scramble in extraction. Try a single-column version for the upload, then keep your visual one separately.