If you have PDFs with fillable fields signed externally (outside of RentRedi), you will to export as a PDF without fillable form fields before uploading them to RentRedi.
Export from Adobe Acrobat, Preview, (or similar) as a read-only (or static) PDF without fillable form fields.
For Preview:
Open the PDF file in Preview that you want to make static. If you have another app set to open your PDF files, simply right-click the file and select Preview from the Open with menu.
From the File menu, select the “Export to PDF” option.
Save the file
For Adobe Acrobat Pro*:
Save a copy of the PDF
Open the copy of the PDF
Save As Optimized PDF
Go to Discard Objects
Check Flatten Form Fields box
Click on Okay to save as a regular uneditable PDF