In Adobe Acrobat 9, I was able to select a table, right-click on the selection, choose “Copy As Table…”, and then paste that table into Excel (right-click on a cell, select “Paste Special…”, and choose “XML Spreadsheet”). In Acrobat X, the same actions result in a one row table in Excel with the column values from all rows concatenated together. The resulting table is useless.
The best guess as to the cause is that Acrobat X incorrectly interprets the table tags. This problem has been known since at least the beginning of 2011 but unfortunately, Adobe has not provided a fix in even the most recent version of Acrobat X. While there are several solutions, including manually altering the table tags (so that Acrobat X would recognize the table) or exporting first to a Word document then doing the copy-paste from Word to Excel, the simplest solution I found was to copy the table column by column to Excel.
To select just the column in Acrobat X, hold down the Alt button and click-drag to highlight one table column. Use the normal copy command (Ctrl-C or right-click on the selection and choose Copy) to copy the column. Do not use the “Copy As Table…” command because it may result in corrupted or missing column values. In Excel, use the normal Paste command (Ctrl-V or right-click on the first field and choose Paste); actually, the “XML Spreadsheet” special paste option won’t be available for selection at all. Repeat the above for each of the remaining columns.
I found the column-by-column copy-paste approach to work great for small tables. If you have a huge table to copy, you may wish to use another method (for example, converting the PDF to Word and then copy-pasting the table from Word to Excel).
The copy-paste table methods described above and others were found in the comments at How to copy/Paste a table from PDF to Excel using AcrobatX.