I can only try to tell what I normally do in your situation.
Load the scanned image/page into windows paint. Copy it and paste it in MS Office Word. Hope u do have it.
Now repeat that for every page. Off course you have to put a page break at end of each page to get the next page.
If the scanned image/page is larger than the standard MS Office Word page, then you can do 1 or both of the following:
1. Resize the image/page in Win Paint and / or
2. Adjust the margins in MS Office Word to Narrow margins
Depending on which version of MS Office(assuming you have it) you can then save it as a .pdf file.