You would need to fix these accessibility issues in Acrobat. Below I include the explanation on how to fix the errors, taken from the Acrobat XI Help document at:
To make these changes in Acrobat XI, first save a copy of the FormsCentral document. Make the accessibility fixes, and then save the document via File menu -> Save As Other -> Reader Extended PDF -> Enable More Tools (includes form fill-in & save).
1. All of the text on this page lacks a language specification.
Setting the document language in a PDF enables some screen readers to switch to the appropriate language. This check determines whether the primary text language for the PDF is specified. If the check fails, set the language.
To set the language automatically, select Primary Language in the Accessibility Checker tab, and then choose Fix from the Options menu. Choose a language in the Set Reading Language dialog box, and then click OK.
To set the language manually, do one of the following:
• Choose File > Properties > Advanced and then select a language from the pop-up menu in the Reading Options section. (If the language doesn't appear in the pop-up menu, you can enter the ISO 639 code for the language in the Language field.) This setting applies the primary language for the entire PDF.
• Set the language for all text in a subtree of the tags tree. Open the Tags panel. Expand the Tags root and select an element. Then choose Properties from the Options menu. Choose a language from the Language pop-up menu. (To display the Tags panel, choose View > Show/Hide > Navigation Panes > Tags.)
• Set the language for a block of text by selecting the text element or container element in the Content panel. Then, right-click (Windows) or Ctrl-click (Mac OS) the text and choose Properties from the context menu. (To display the Content panel, choose View > Show/Hide > Navigation Panes > Content.2)
2. 5 form fields(s) with no description
For accessibility, all form fields need a text description (tool tip).
To add a text description to a form field:
1. Select one of the Form tools, and then right-click (Windows) or Ctrl-click (Mac OS) the form field.
2. Choose Properties from the context menu.
3. Click the General properties tab.
4. Enter a description of the form field in the Tooltip field.
3. Tab order may be inconsistent with the structure order.
Because tabs are often used to navigate a PDF, it's necessary that the tab order parallels the document structure.
To fix the tab order automatically, select Tab Order on the Accessibility Checker panel, and choose Fix from the Options menu.
To manually fix the tab order for links, form fields, comments, and other annotations:
1. Click the Pages panel on the navigation pane.
2. Click a page thumbnail, and then choose Page Properties from the Options menu.
3. In the Page Properties dialog box, choose Tab Order. Then, select Use Document Structure, and click OK.
4. Repeat these steps for all thumbnails in the document.