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DataDear can attach sheets in the same workbook. Attaching a pdf can be done if you copy the pdf inside the sheet as an object:
Embed an object in a worksheet
Click inside the cell of the spreadsheet where you want to insert the object.
On the Insert tab, in the Text group, click Object .
In the Object dialog box, click the Create from File tab.
Click Browse, and select the file you want to insert.
If you want to insert an icon into the spreadsheet instead of show the contents of the file, select the Display as icon check box. If you don’t select any check boxes, Excel shows the first page of the file. In both cases, the complete file opens with a double click. Click OK.
More on how attachments work can be found here - How do I upload attachments when creating and editing records?