Oracle reports has two main issues where we can fix the same using the below two steps.

1. if the generated PDF file has alignment issues in some of the PDF viewer then apply the patch which contains rw.dll file
2. if the generated PDF file has large file size (1.5Mb or 2MB) then set 25 in REPORTS_JPEG_QUALITY_FACTOR environment variable on the server. this will happen mainly when you are attaching the image on the report file like HBL terms

both are simple issues which creates major problem with oracle report users.